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THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 

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^OJIIVDJO- 


A  TREATISE 


MOTOR  APPARATUS  OF  THE  EYES 

EMBRACING  AN  EXPOSITION  OF  THE 

ANOMALIES  OF  THE  OCULAR  ADJUSTMENTS 
AND  THEIR  TREATMENT 


WITH   THE 


ANATOMY  AND  PHYSIOLOGY  OF  THE  MUSCLES 
AND  THEIR  ACCESSORIES 


GEORGE  T.  STEVENS,  M.D.,  PH.D. 


flllustrateo  witb  184  Engravings,  gome  in  Colors 


PHILADELPHIA 

F.  A.   DAVIS  COMPANY,   PUBLISHERS 
1906 


COPYRIGHT,  1906, 

BY 

F.  A.  DAVIS  COMPANY 

f  Registered  at  Stationers'  Hall,  London,  England.] 


Philadelphia,  Pa.,  U.S.A.: 

Press  of  F.  A   Davis  Company 

1916  Cherry  Street. 


Btomedfatf 
Library 

w  w 


PREFACE. 


WHEN,  in  my  work  on  "Functional  Xervous  Diseases,"  published 
in  1884,  I  intimated  that  it  would  be  followed  by  one  on  the  "Anom- 
alies of  the  Muscles  of  the  Eyes,"  my  purpose  was  to  compile  the  facts 
and  views  extant  at  that  time.  It  then  seemed  that  such  a  compilation, 
including  the  few  new  suggestions  which  I  had  myself  advanced, 
would  constitute  a  valuable  accession  to  the  working  means  required  in 
treating  many  forms  of  nervous  disturbances. 

The  work  was  commenced,  but  it  soon  appeared  that  much  was 

to  be  learned  in  this  field  and  that  it  would  be  wiser  to  publish  the 

-  ~~  —  ~™a  +n  TTIP  to  have  been  settled  by  my  own  inves- 

,  in  the  expectation  that, 

t  be  assembled  into  book 
ERRATA. 


I"  f  <*?  'Stique'  read  d'°™»«^-  ing  the  subject  as  it  then 

footnote,  for  ^Xcrytew,  read  7r\dyl0s  ,.  , 

Page  119,  Hue  23,  for  Spherical,  read  Plane    '  '      A"   theSG    artld6S    EP~ 

Page  436,  footnote,  for  wwrrdfc,-,  read  vewrdfyiv  cllives  of  Ophthalmology 

Page  436,  footnote,  for  ToXdwwfcj,  read  TdMrruru.  erest  in  the  subject  was 


xne  ssuuj^v,^--—  _____^_|.^_  nder  the  teachings  of  ex- 

perience and  the  closer  investigation  of  the  principles  underlying  the 
phenomena,  that  the  publication  of  the  work  as  a  whole  seemed  further 
and  further  from  realization.  Several  times  the  work  has  appar- 
ently been  ready  for  presentation,  yet  as  often  new  light  has  been 
thrown  upon  the  facts  already  known  in  such  manner  as  to  make  delay 
still  desirable. 

At  length,  while  I  do  not  by  any  means  imagine  that  the  subject 
is  advanced  to  its  limit,  for  nothing  is  more  true  than  that  the 
answering  of  a  question  in  science  only  opens  the  way  for  other  ques- 
tions, I  believe  that  a  good  purpose  will  be  served  by  presenting  in  a 
systematic  form  the  principles  which  appear  to  me  to  govern  the 
physiological  actions  and  the  anomalous  disturbances  of  the  motor 
apparatus  of  the  eyes.  Whatever  progress  may  be  made  in  future 

(Hi) 

635919 


COPYRIGHT,  1906. 


[Register 


Philadelphia,  Pa.,  U.S.A.: 

Press  of  F.  A  Davis  Company 

1916  Cherry  Street. 


Bwmedierf 

Library 

w  w 

i+oo 


PREFACE. 


N,  in  my  work  on  "Functional  Xervous  Diseases,"  published 
in  1884,  I  intimated  that  it  would  be  followed  by  one  on  the  "Anom- 
alies of  the  Muscles  of  the  Eyes,"  my  purpose  was  to  compile  the  facts 
and  views  extant  at  that  time.  It  then  seemed  that  such  a  compilation, 
including  the  few  new  suggestions  which  I  had  myself  advanced, 
would  constitute  a  valuable  accession  to  the  working  means  required  in 
treating  many  forms  of  nervous  disturbances. 

The  work  was  commenced,  but  it  soon  appeared  that  much  was 
to  be  learned  in  this  field  and  that  it  would  be  wiser  to  publish  the 
principles  which  appeared  to  me  to  have  been  settled  by  my  own  inves- 
tigations and  experience  in  occasional  articles,  in  the  expectation  that, 
at  a  later  period,  the  substance  of  these  might  be  assembled  into  book 
form. 

A  series  of  articles,  progressively  developing  the  subject  as  it  then 
presented  itself,  was  consequently  published.  As  these  articles  ap- 
peared from  time  to  time,  mostly  in  the  Archives  of  Ophthalmology 
and  Annals  c'Oculistique,  a  very  general  interest  in  the  subject  was 
awakened  both  in  America  and  in  Europe. 

The  subject,  however,  grew  so  rapidly  under  the  teachings  of  ex- 
perience and  the  closer  investigation  of  the  principles  underlying  the 
phenomena,  that  the  publication  of  the  work  as  a  whole  seemed  further 
and  further  from  realization.  Several  times  the  work  has  appar- 
ently been  ready  for  presentation,  yet  as  often  new  light  has  been 
thrown  upon  the  facts  already  known  in  such  manner  as  to  make  delay 
still  desirable. 

At  length,  while  I  do  not  by  any  means  imagine  that  the  subject 
is  advanced  to  its  limit,  for  nothing  is  more  true  than  that  the 
answering  of  a  question  in  science  only  opens  the  way  for  other  ques- 
tions, I  believe  that  a  good  purpose  will  be  served  by  presenting  in  a 
systematic  form  the  principles  which  appear  to  me  to  govern  the 
physiological  actions  and  the  anomalous  disturbances  of  the  motor 
apparatus  of  the  eyes.  Whatever  progress  may  be  made  in  future 

(Hi) 

635949 


jv  PEEFACE. 

will  not,  I  believe,  supplant  the  general  principles  which  I  have  here 
formulated,  hut  will,  I  trust,  serve  to  explain  many  questions  which 
can  not  now  be  answered. 

In  the  domain  of  anatomy  I  have  endeavored  to  present  known 
facts  as  I  have  found  them  in  the  works  of  others,  adding  very  little 
of  my  own.  My  purpose  has  been  to  set  these  facts  more  clearly  and 
concisely  before  the  reader  than  has  been  done  before. 

In  the  physiological  division,  while  endeavoring  to  set  forth  the 
essential  doctrines  which  have  been  to  an  important  extent  accepted, 
I  have  not  hesitated  to  place  new  interpretations  upon  known  phe- 
nomena, and  I  have  advanced  a  number  of  entirely  new  views  while 
placing  some  of  the  older  views  in  new  light. 

It  is  in  the  field  of  systematizing  and  elucidating  the  principles 
upon  which  the  anomalies  of  the  motor  apparatus  of  the  eyes  depend 
that  I  have  presented  a  system  which,  while  originally  based  upon 
older  knowledge,  has  so  far  deviated  from  the  original  views  that  the 
whole  system  may  be  regarded  as  new,  except  as  it  has  been  from  time 
to  time  stated  by  myself. 

In  the  division  devoted  to  paralytic  and  obstructive  affections  of 
the  eye  muscles  I  have  compiled  in  a  condensed  form  the  principal 
facts  as  they  have  been  advanced  by  many  observers. 

The  work  is  a  sequel  to  that  on,  "Functional  Nervous  Diseases."' 
It  is  believed  that  a  practical  acquaintance  with  the  principles  and 
practice  included  here  will  promote  the  more  systematic  development 
of  the  central  doctrine  of  that  work,  which  Avas,  difficulties  of  adjust- 
ments of  the  eyes  are  a  source  of  nervous  trouble  and  more  frequently 
than  other  conditions  constitute  a  neuropathic  tendency. 

This  proposition  was,  when  it  was  announced  by  myself,  absolutely 
new  both  as  to  the  statement  that  such  difficulties  of  adjustment  con- 
stitute a  neuropathic  tendency  and  as  to  the  comparative  importance 
of  this  source  of  disturbance.  An  experience  of  nearly  thirty  years 
has  fully  confirmed  this  proposition  and  I  have  no  hesitation  in  re- 
stating it  here. 

In  view  of  this  proposition  a  knowledge  of  the  principles  of  the 
adjustments  of  the  eyes  and  their  anomalies  becomes  of  greatest  im- 
portance. 

GEORGE  T.  STEVENS. 

NEW  YORK,  1906. 


TABLE  OF  CONTENTS. 


INTRODUCTION. 

HISTORICAL  XOTES  OF  STRABISMUS  AND  OTHER  ANOMALIES  OF  THE 

EYE  MUSCLES.  PAGE 

First  Period — Strabismus 1 

Second  Period — Heterophoria 14 

PAET  I. 

ANATOMY  OF  THE  MOTOR  MUSCLES  OF  THE  EYES  AND  OF  THE  PARTS 
ACCESSORY  TO  THEM. 

SECTION  I. 

Movements  and  Position  of  the  Eyes 28 

Position  of  the  Eyes  in  Animals 28 

SECTION  II. 

Comparative  Anatomy  of  the  Eye  Muscles 29 

Peculiarities  of  the  Eye  Muscles  in  Fishes 29 

Peculiarities  in  Amphibious  Reptiles 30 

Peculiarities   in  Birds 32 

Peculiarities  in  Mammals 33 

SECTION  III. 

The   Orbits 35 

Measurements  of  the  Orbits 39 

Plane  of  the  Optic  Axis 44 

Orbital  Axes  in  Ethnology 46 

Contents  of  the  Orbits 47 

SECTION  IV. 

The    Muscles 48 

The  Internal  Rectus 50 

The   External  Rectus 51 

The  Superior  Rectus 51 

The  Inferior  Rectus 51 

The  Superior  Oblique 52 

The  Inferior  Oblique 53 

SECTION  V. 

Insertions   of  the   Tendons 54 

SECTION  VI. 

The  Capsule  of  Tenon  or  Orbito-Ocular  Aponeurosis 61 

Internal  or  Bulbar  Capsule . 64 

External  Capsule  or  External  Aponeurosis 65 

Ligamentous  Ailerons  or  Bridles — Orbital  Muscles 67 

General  Considerations  Regarding  the  Ailerons  and  Aponeurosis 68 

(V) 


Vi  TABLE  OF  CONTENTS. 

SKCTION  VII.                                                                                                        PAGK 
The  Vessels  Supplying  the  Muscles  of  the  Eyes 69 

SKCTION  VIII. 

The  Nerves  of  the  Muscles 71 

SECTION  IX. 

Nuclear  Origin  of  the  Nerves  of  the  Ocular  Muscles 76 

SECTION  X. 

Circulation  to  the  Nuclei  of  the  Nerves  of  the  Ocular  Muscles 84 


PART  II. 

PHYSIOLOGY. 

SECTION  XI. 

The  Centre  of  Movements  of  the  Ocular  Globe  ........................   86 

SECTION  XII. 

Definitions  of  Terms  Employed  in  Describing  the  Positions  and  Divisions 
of  the  Head  and  of  the  Relations  of  the  Eyes  and  of  Objects  Seen 
to  the  Head  ....................................................  90 

SECTION  XIII. 

Direction  of  the  Influence  of  the  Various  Motor  Muscles  of  the  Eyes  .  .  93 
Resume  of  the  Movements  of  Each  Eye  Singly  .......................  102 

Associated  Movements  of  the  Eyes  ...................................  103 

SECTION  XIV. 

Some  of  the  Phenomena,  Causes  and  Laws  of  Torsions  of  the  Eyes  ....  106 
Accidental  Images  ..................................................  115 

SECTION  XV. 

Visual  Perception  of  Space  ..........................................  124 

SECTION  XVI. 

Perspective  .......................................................  137 

SECTION  XVII. 
.         The  Stereoscope,  the  Stereostroboscope  and  the  Pseudoscope  ..........  143 

SECTION  XVIII. 

Unconscious   Conclusions  ............................................  153 

SECTION  XIX. 

The  Field  of  Binocular  Vision  ........  ................................  164 

SECTION  XX. 

Of  Corresponding  Points  ............................................  1" 


SECTION  XXI. 

The   Horopter  ......................................................  17' 

SECTION  XXII. 

The  Directions  of  the  Apparent  Vertical  and  Horizontal  Meridians  .....  19 

SECTION  XXIII. 

Voluntary  Torsion  and  its  Physiological  Effects  ......................  200 


TABLE  OF  CONTENTS.  vii 

SECTION  XXIV.  PAGE 

The  Normal  Direction  of  the  Planes  of  Vision  in  Relation  to  Certain 

Cranial  Characteristics.  .  203 


PART  III. 

ANOMALOUS    CONDITIONS   OF   THE   MOTOR   MUSCLES   OF   THE   EYES 
CONSISTENT  WITH  THE  PHYSIOLOGICAL  STATE. 

SECTION  XXV. 

Synopsis  of  the  Classification 214 

SECTION  XXVI. 

Exposition  of  the  Classes 217 

Class  I. 

Relations   of    the   Normal   Plane   of  Vision   of  the   Individual   to   the 

Cranium 217 

Anophoria  and  Katophoria 217 

Anotropia  and  Katotropia 223 

SECTION  XXVII. 

Determination  of  the  Extent  of  the  Rotations  of  the  Eyes 225 

The   Tropometer 225 

Treatment  of  Anophoria  and  Katophoria 231 

SECTION  XX VII  I. 
Class  II. 

Declinations,  or  the  Normal  Declinations  of  the  Retinal  Meridians.  ..  .233 

Instruments  for  Determining  Declinations 237 

Some  of  the  Relations  Between  Declinations  and  Heterophoria 242 

Empirical  Scheme  for  some  of  the  Relations  of  Declination  and  Hetero- 
phoria   245 

Heterotropia,  or  Strabismus  and  Declination 248 

Local  Symptoms  of  Declinations 249 

Astigmatism  and  Myopia 251 

Declinations,  the  Contour  of  the  Brows  and  the  Relative  Positions  of 

the  Eyes 252 

Pose  of  the  Head  from  Declination 254 

Other  Symptoms 255 

Treatment   of  Declinations 256 

SECTION  XXIX. 
Class  III.     . 
Accommodative  Axial  Adjustments 257 

SECTION  XXX. 

Difference  of  Degree  of  Anomalous  Conditions  of  the  Motor  Muscles.  .  .258 

SECTION  XXXI. 

Equilibrium 260 

SECTION  XXXII. 

Orthophoria 261 

SECTION  XXXIII. 

Heterophoria 261 


viii  TABLE  OF  CONTENTS. 

SECTION  XXXIV.                                                                                                  PAGK 
Principles  of  Examination  in  Heterophoria 263 

SECTION  XXXV. 

Significance  of  Heterophoric  Conditions 270 

SECTION  XXXVI. 

Time  for  Attending  to  the  Anomalies  of  Heterophoria 271 

SECTION  XXXVII. 

Specific  Methods  and  Instruments  for  Examinations  in  Heterophoria.  .272 

SECTION  XXXVIII. 

Esophoria 286 

SECTION  XXXIX. 

Exophoria 288 

SECTION  XL. 

Hyperphoria 291 

SECTION  XLI. 

Nature  and  Causes  of  Heterophoria 297 

SECTION  XLII. 

Summary  of  Procedure  in  Examinations  for  Heterophoria,  Anophoria, 
Katophoria  and  Declinations 302 

SECTION  XLIII. 

Clinical    Features    of    the    Non-Strabismic    Anomalies    of    the    Ocular 
Muscles 306 

SECTION  XLIV. 

Facial  Expressions  Resulting  from  the  Conditions  of  the  Eye  Muscles.  .318 

SECTION  XLV. 

General  Treatment  of  Non-Strabismic  Anomalies 327 

The  Use  of  Prisms 330 

Gymnastics  for  Declination 331 

Prisms  Worn  as  Spectacles 333 

Decentering  of   Spherical  and   Cylindrical   Glasses  for  Obtaining  Pris- 
matic Effect 334' 

SECTION  XLVI. 

Surgical   Treatment 336 

Operative  Treatment  of  Declinations 340 

Procedure  in  Anophoria  and  Katophoria 345 

Operative  Treatment  for  Heterophoria 347 

Graduated  Tenotomy 348 

Tendon  Contraction 352 

SECTION  XLVII. 

Heterotropia — Strabismus   354 

Deviation  in  Exclusion 372 

Tests   by  Diplopia 373 

SECTION  XLVIII. 

Esotropia — Converging    Strabismus 378 

Exotropia — Diverging    Strabismus 382 

Hypertropia — Strabismus     Sursumvergens 384 


TABLE  OF  CONTENTS.  ix 

SECTION  XLIX.                                                                                                              PAGE 
Anotropia  and  Katotropia — The  Two  Forms  of  Double  Vertical  Stra- 
bismus   388 

SECTION  L. 

Periodic   or   Intercurrent   Strabismus 393 

SECTION  LI. 

Causes   of   Strabismus 395 

SECTION  LIT. 

The  Relations  of  the  Function  of  Accommodation  to  that  of  Convergence  397 

SECTION  LIII. 

Heredity  of  Strabismus 407 

SECTION  LIV. 

A  Table  of  Strabismus  Cases 408 

SECTION  LV. 

Treatment   of   Strabismus 414 

Surgical    Treatment 418 

The  Empirical  Method 421 

SECTION  LVI. 

Results  of  Treatment  of  Strabismus 422 

SECTION  LVII. 

Resume  of  the  Operative  Treatment  of  Strabismus 423 

SECTION  LVIII. 

Antipathy  to  Single  Vision 426 

SECTION  LIX. 
Class  IV. 

Nystagmus — Talantropia    436 


PART  IV. 

ANOMALOUS  CONDITIONS  OF  THE  MOTOR  APPARATUS  OF  THE  EYES 
NOT  CONSISTENT  WITH  THE  PHYSIOLOGICAL  STATE. 

SECTION  LX. 
Class  V. 

Colytropia — Spasm,  Paralysis,  Obstruction,  etc 444 

SECTION  LXI. 

Spasm.     Spasmodic    Colytropia 446 

Word  Blindness.     Psychic  Colytropia 450 

SECTION  LXII. 

Paralysis.     Paralytic    Colytropia 452 

Paralysis  of  the  External  Rectus 455 

Paralysis  of  the  Internal  Rectus 457 

Paralysis  of  the  Superior  Rectus 457 

Paralysis  of  the  Inferior  Rectus 460 

Paralysis  of  the  Superior  Oblique 460 

Paralysis  of  the  Inferior  Oblique 464 


x  TABLE  OF  CONTENTS. 

SECTION  LXIII.  PAGE 

Relations  of  the  Double  Images  in  Paralysis  of  the  Ocular  Muscles.  . .  .466 

SECTION  LXIV. 

Objective  Manifestations  of  Paralysis  of  the  Ocular  Muscles 466 

SECTION  LXV. 

Limitation  of  Action  of  the  Paralyzed  Muscle 469 

SECTION  LXVI. 

Measurement  of  the  Deviations  of  Paralysis 469 

SECTION  LXVII. 

Nuclear    Paralysis 470 

Nuclear  Paralysis  of  the  Oculo-Motor  Nerve 474 

Total  Oculo-Motor  Paralysis 475 

SECTION  LXVI1I. 

Causes  of  Nuclear  Paralysis 479 

SECTION  LXIX. 

Fascicular    Paralysis 483 

Peripheral   Paralysis 485 

SECTION  LXX. 

Obstructive    Colytropia 485 

SECTION  LXXI. 

Traumatic    Colytropia 486 

SECTION  LXXII. 

Arrested  Development  of  Ocular  Muscles 487 

SECTION  LXXIII. 

Treatment   of  Colytropia 488 


LIST  OF  ILLUSTRATIONS. 


FK*.  PAGE 

Portrait  of  Dr.  John  Taylor Facing  26 

1.     Eye  Muscles  of  Cod  (Morrhua  Americana).     (Colored) 30 

2      Head  of  a  Frog  (Rana  fontinalis.  Showing  the  Muscles  of  One  of  the 

Eyes.     (Colored.)      31 

3.  Head  of  Winter  Gull  (Lams  argentatus),  Showing  a  Dissection  of  the 

Eye  Muscles.     (Colored.) 33 

4.  The  External  Muscles  of  the  Eye  of  the  Domestic  Sheep.     (Colored.)  34 

5.  The  Orbits .  36 

6.  The  External  Wall  of  the  Orbit 37 

7.  The  Internal  Wall  of  the  Orbit 38 

8.  Vertical  and  Transverse  Diameters  of  the  Orbit 41 

9  to  11.     Characteristic  Forms  of  the  Orbits 44 

12.  Stevens's  Craniostat  for  the  Examination  of  the  Planes  of  the  Orbit  .  45 

13.  The  Motor  Muscles  of  the  Eyes.     (Colored) 49 

14.  Schwalbe's  Scheme  of  the  Origin  of  the  Eye  Muscles  at  the  Posterior 

Portion  of  the  Orbit  of  the  Right  Eye 50 

15.  Diagrams  Indicating  the  Insertions  of  the  Muscles  in  Three  Pairs  of 

Eyes  of  Young  Persons 57 

16      Design  by  the  Author  to  Indicate  the  Relative  Insertions  of  the  Differ- 
ent Muscles  into  the  Sclera 59 

17.  Diagram  Indicating  the  Arrangement  of  the  Capsule  of  Tenon,  from  a 

Side  View.     ("Colored) 62 

18.  Investment  of  the  Muscles  of  the  Eye  by  the  Capsule  of  Tenon    ...  64 

19.  1,  Sclera.     2,  Tendon.     3,  Fold  of  the  Capsule.     4,  External  Layer  of 

the  Capsule 66 

20.  Arteries  Supplying  the  Muscles  of  the  Eye.     (Colored) 70 

21.  Distribution  of  the  Nerves  of  the  Muscles  of  the  Eyes.     (Colored).    .  71 

22.  Diagram  Indicating  the  Origin  of  the  Third  and  Fourth  Nerves   ...  73 

23.  Diagrammatic  Representation  of  Mid-brain  with  Approximate  Situa- 

tions of  the  Nuclear  Groups  from  which  Arise  the  Third,  Fourth, 

Fifth,  and  Sixth  Nerves 75 

24.  Scheme  Showing  the  Different  Groups  of  Nervous  Cells  which  Consti- 

tute the  Nuclear  Origin  of  the  Common  Oculo-motor  Nerve  ...  77 

25.  Professor  Bernheimer's   Diagram  of  the   Nucleus  of   the  Oculomotor 

and  of  the  Trochlearis  Nerves.     (Colored) 81 

26.  Bernheimer's  Diagram  of  the  Connections  of  the  Nuclei  of  the  Oculo- 

motor Nerve  and  the  Cortex 82 

27.  Arteries  Supplying  the  Pons  Varolii  and  Mid-brain 85 

28.  Position  of  Images  as  shown  by  Ophthaluiometer 88 

xi 


xij  LIST  OF  ILLUSTRATIONS. 

FIG.  PAGE 

29.  Planes  of  the  Head 91 

30.  Diagram  Indicating  the  Traction  Direction  of  the  Lateral  Recti  with 

the  Axis  of  Rotation  by  these  Muscles 93 

31.  Direction  of  Traction  of  the  Superior  and  Inferior  Rectus  and  the  Axis 

of  Rotation  by  them 97 

32.  Position  of  Vertical  Meridian  of  the  Cornea  with  Different  Directions 

of  the  Eye 99 

33.  Direction  of  Traction  of   the  Superior  and  Inferior   Oblique   Muscles 

with  the  Axis  of  Rotation 100 

34.  35.     Stevens's  Ophthalmotrope 114 

36,37.     Positions  of  Accidental  Images.     (Colored) 116 

38.  Diagram  from  Helmholtz 117 

39.  Position  of  Accidental  Images  from  a  Vertical  Line 118 

40.  Illustration  of  Correspondence  of  the  Images 123 

41.  Illusion  of  Height  and  Breadth  . 132 

42.  The  Muller-Lyer  Illusion 132 

43.  Geometric  Illusion,  after  Hering 133 

44.  Geometric  Illusion,  after  Wundt 133 

45.  Zollner's  Figure 134 

46.  Diagram  Illustrating  Angle  of  Movement 135 

47.  Geometric  Illusion,  after  Lehmann 136 

48.  Poggendorff  Illusion     . 137 

49.  Schroder's  Diagram 139 

50.  Diagram  representing  the  principle  of  Wheatstone's  Stereoscope   .    .    .  144 

51.  Brewster's  Stereoscope.     (Colored) 145 

52.  Diagram  Illustrating  Blending  of  Images 147 

53.  Landolt's  Stereoscope  for  Reestablishing  Binocular  Vision 149 

54.  The  Stereostroboscope 150 

55.  Wheatstone's  Pseudoscope 152 

56  to  61.     Stereoscopic  Diagrams 156,158,160,161,162,163 

62.  The  Common  Field  of  Vision      165 

63.  Maculas  and  Corresponding  Points  According  to  the  Accepted  Doctrine  168 

64.  Volkmann's  Diagram .  170 

65.  Retinal  Corresponding  Points 171 

66.  Diagram  Illustrating  Different  Positions  of  Images 174 

67.  Helmholtz's  Figure  Indicating  the  Position  of  the  Horopter  when  the 

Eyes  are  directed  toward  the  Horizon 179 

68  to  73.     Diagrams  for  Ascertaining  the  Horopter ....  185,  186,  187,  188,  189 

74.  Clinoscope  Objectives    ...'.', 197 

75.  Diagram  for  Testing  Meridians 198 

76.  Helmholtz's  Squares , 199 

77.  Torsion  Objectives 201 

78.  The  Long  Head,  from  above 205 

79.  The  Tall  Head,  from  above 205 

80.  The  Broad  Head,  from  above 205 

81.  The  Long  Head,  side  view 206 

82.  The  Tall  (Medium)  Head,  side  view    . 206 

83.  The  Broad  Head,  side  view 206 


LIST  OF  ILLUSTRATIONS.  xiii 

FIG.  PAGE 

84.  Broca's  Calipers 206 

85.  Author's  Facial  Goniometer 207 

86.  The  Author's  Method  of  Determining  the  Axis  of  the  Orbit 208 

87.  Front  View  of  Long  Skull 209 

88.  Front  View  of  Tall  Skull 209 

89.  Front  View  of  Broad  Skull 209 

90.  Stevens's  Tropometer 226 

91.  The  Tropometer  Scale 227 

92.  93.     Before  and  After  Correction  of  Katophoria 232 

94.  Diagram  Illustrating  Declination 235 

95.  The  Cliuoscope 238 

96.  Objective  Lines  for  the  Clinoscope 239 

97.  The  Lens  Clinoscope 239 

Method  of  Testing  the  Clinoscope 240 

98  to  101.     Diagram  Illustrating  Relations  of  Declination  and  Heterophoria. 

(Colored) 246,  247 

102.  Diagram  Illustrating  Diplopia  Induced  by  Prism 264 

103.  Diagram  Illustrating  Diplopia 265 

104.  Author's  Phorometer 273 

105.  Author's  Improved  Rotating  Prism  Slide 274 

106.  Maddox  Rod 276 

107.  Author's  Stenopaic  Lens 277 

108.  Form  of  Images  by  the  Author's  Stenopaic  Lens       278 

109.  The  Long  Head  with  Prognathous  Face 314 

110  to  113.     Carriage  of  Head  with  Various  Peculiarities  of  Adjustments  of 

Eyes 316,  317 

114.  Expression  of  Eyebrows 319 

115,  116.     Asymmetrical  Positions  of  Eyes  in  Declination 320 

117,  118.     Expressions  of  Eyebrows 321,  322 

119.  Typical  Adjustment  of  the  Facial  Muscles  with  Orthophoria 323 

120.  Typical  Adjustment  of  the  Facial  Muscles  with  Exophoria 323 

121.  Typical  Adjustment  of  the  Facial  Muscles  with  Exophoria 324 

122.  Typical  Adjustment  of  the  Facial  Muscles  with  Hyperphoria    ....  324 

123.  124.     With  a  High  Degree  of  Esophoria 326 

125,126.     With  Typical  Expressions  of  Exophoria 326 

127,  128.     Before  and  After  Correction  of  Hyperexophoria 327 

129.  The  Rod  Clinoscope 332 

130.  Objectives  for  Clinoscope      332 

131.  Diagram  Illustrating  Decentering  of  Lens  for  Prismatic  Effect ....  335 

132.  Diagram  Illustrating  the  Change  of  the  Line  of  Insertion  of  the  Ten- 

don of  the  Interims 342 

133.  Flexible  Eye  Speculum 343 

134.  Lid  Retractor 343 

135.  Fine  Forceps 343 

136.  Scissors 343 

137.  Fine,  Sharp  Hook 343 

138.  Small  Tendon  Hook 343 

139.  Grooved  Director 343 


xiv  LIST  OF  ILLUSTRATIONS. 

FIG.  PAGE 

140.  Needle-holder 343 

141.  Lance  Probe 343 

142.  Catch  Forceps 343 

143.  Diagram  of  Stevens's  Operation  for  Teuotomy 349 

144.  Diagrammatic  Representation  of  von  Graefe's  Operation  for  Tenotomy  350 

145.  146.     Diagrams  Illustrating  Deviations  of  the  Eye                                  363,  364 
147  to  149.     Two  Cases  of  Convergent  Strabismus  and  One  of  Paralysis    .    .  380 
150,  151.     Indicating   the   Compound   Direction   of   the    Deviating   Eye   in 

Diverging  Strabismus       383 

152.  Left  Eye  in  Fixation,  Right  Deviating  up 391 

153.  Right  Eye  in  Fixation,  Left  Deviating  up 391 

154  to  157.     Cases  of  Converging  Strabismus  Depending  on  Vertical  Devia- 
tions and  after  Treatment  Directed  to  the  Superior  Recti  only  .    .  392 

158,  159.     Showing  the  Correction  of  a  Converging  Strabismus  by  a  Weak 

Prism  with  its  Base  Down 400 

160  to  162.     Influence  of  a  Convex  Glass  in  Correcting  an  Inward  Deviation  401 

163  to  165.     Various  Forms  of  Deviation,  Depending  on  Choice  of  Fixation  .  404 

166.  Insertion  of  Tendons 406 

167,  168.     A  Case  of  Strabismus  at  Different  Periods  of  Life  419 
169,  170.     Results  of  Over-correction  of  Converging  Strabismus 426 

171.  A  Case  of  Converging  Strabismus  which  Changed  to  Diverging  Strabis- 

mus in  Later  Life 431 

172.  Slight    Diverging  Strabismus    Succeeding   the    Convergence    Seen    at 
Fig.  171 431 

173.  Diverging  Strabismus   Converted  into  the   Converging  Form  by   the 

Instillation  of  Atropine   ....        , 432 

174.  N  Diverging  Strabismus   which   in   Youth  Became   Marked   Converging 

Squint 433 

175.  Motor  Area  for  the  Eyes,  according  to  Beevor  and  Horsley 449 

176.  177.     Paralysis  of  External  Rectus,  Left  Eye 456 

178,  179.     Paralysis  of  Superior  Rectus  of  Right  Eye 457 

180.  Diagram  Indicating  the  Relative  Positions  of  the  Images  in  Paralysis 

of  Individual  Muscles  of  the  Right  Eye 468 

181.  Arm  of  Stevens's  Perimeter 470 

182.  Professor  Beruheimer's  Diagram   of   the   Nucleus  of   the   Oculomotor 

and  of  the  Trochlearis  Nerve 473 

183.  Ophthalmoplegia  Externa  in  an  Adult 476 

184.  Paralysis  of  the  Third  Nerve  in  a  Child 478 


HISTORICAL  XOTES   OF   STRABISMUS   AXD   OTHER 
ANOMALIES  OF  THE  EYE  MUSCLES.1 

ONLY  the  notable  defects  in  the  directions  of  the  eyes  were  likely 
to  have  been  taken  into  account  by  the  ancients.  The  lesser  anomalies 
were  unobserved  until  very  recent  times. 

Of  the  notably  conspicuous  defects  there  was  the  dubious  gaze 
of  the  diverging  squint;  then  there  was  the  sinister  and  contracted 
visage  of  the  converging  squint,  and  lastly  there  was  the  convenient 
vertical  squint  that  enabled  its  possessor  to  keep  "one  eye  on  the  pot 
and  the  other  up  the  chimney." 

Only  these  forms  of  deviation  from  the  positions  most  agreeable 
to  see  claimed  the  attention  of  the  observer  until  quite  within  our 
own  day. 

We  may  then  divide  our  subject  into  two  periods  of  time,  each 
of  which  will  be  characterized  by  the  forms  of  defect  observed.  Thus, 
the  first  period  will  be  that  of  the  recognition  of  strabismic  affections, 
while  the  second  period  will  include  also  the  recognition  and  study 
of  the  lesser  affections,  which  are  now  known  as  those  of  heterophoria. 

FIRST  PERIOD — STRABISMUS. 

In  the  earliest  medical  writings  mention  is  made  of  strabismus. 
Yet,  as  it  was  in  the  times  of  those  early  writings  regarded  as  a  per- 
manent deformity  rather  than  as  a  defect  which  might  yield  to  treat- 
ment, only  meager  space  was  assigned  to  its  discussion. 

Hippocrates,  whose  works  date  about  twenty-two  centuries  ago, 
mentions  distortion  of  the  eyes  as  one  of  the  consequences  of  epilepsy 
in  children.-  He  also  recognizes  it  as  an  inherited  defect,  reasoning 
that,  as  children  with  bald  heads  are  born  to  bald-headed  parents,  so 
parents  with  squinting  eyes  have  also  squint-eyed  children. 


1  This  introduction  was  read  before  the  Western  Ophthalmologic  and  Oto- 
Laryngologic  Association,  at  Xew  Orleans,  February,  1899.  It  has  been 
subjected  to  only  very  slight  revision  in  order  to  adapt  it  to  this  work. 

-  "The  Genuine  Works  of  Hippocrates,"  by  Adams,  New  York,  p.  217. 

(1) 


2  INTRODUCTION. 

Celsus,  in  the  first  century  of  our  era,  devotes  a  short  paragraph 
to  strabismus  and  paralysis  of  the  eye  muscles. 

It  is  only  after  some  centuries  that  we  find  authors  giving  more 
attention  to  the  defect  as  one  susceptible  to  amelioration  by  proper 
treatment. 

Paulus  ^Egineta,  a  celebrated  Greek  medical  writer  of  the  sev- 
enth century,  recommended  the  wearing  of  a  mask  which  should 
•extend  below  the  nose  and  through  which  there  should  be  an  opening 
for  each  eye,  so  placed  as  to  induce  the  eyes  to  assume  direct  positions 
in  order  to  see  through  these  openings. 

And  Ambroise  Pare,  the  pioneer  in  scientific  surgery  of  France,, 
and  whose  works  were  published  from  about  1561  to  1577,  describes 
strabismus  (squint-eyes)  as  a  distortion  of  the  eyes  with  inequality 
of  vision.  It  originates,  he  says,  when  the  cradle  is  placed  in  such 
a  way  that  the  child  sees  the  light  on  one  side,  or  when  the  nurse 
squints  and  the  child  imitates  her.  For  treatment  he  adopts  the 
mask  of  Paulus  JEgineta,  and  he  also  recommends  spectacles  of  horn 
attached  to  a  leathern  band  and  perforated  in  the  middle  of  each  of 
the  discs  of  horn. 

Pare's  etiology  of  squint  has  come  down  through  the  centuries, 
and  even  at  the  present  time  there  are  oculists  who  claim  to  be  en 
rapport  with  modern  ophthalmology  who  gravely  inform  the  parents 
of  their  young  patients  with  devious  directions  of  the  visual  axes  that 
the  fault  was  with  the  cradle  or  with  the  nurse  or  companion. 

Later  still  Antoine  Maitre-Jan1  states  that  some  authors  at- 
tribute the  malady  to  the  crystalline  lens,  believing  that  it  is  situated 
irregularly  or  that  it  is  pushed  to  one  or  the  other  side;  while  other 
authors,  he  says,  regard  the  trouble  as  one  involving  the  whole  eye 
or  attribute  it  to  certain  imaginary  vices  of  the  visual  spirits;  still 
others  regarding  it  as  a  spasm  or  retraction  of  some  of  the  muscles 
of  the  eye. 

The  learned  author  himself  accepts  none  of  these  theories,  but 
places  the  defect  to  the  credit  of  the  cornea  as  one  of  its  many  affec- 
tions. He  comprehends  squinting  in  the  same  class  as  myopia,  and 
says  that  the  two  conditions  are  really  one. 

The  author  then  discourses  learnedly  on  the  refraction  and  adds 
that  it  follows  also  that  those  who  squint  see  objects  larger  than  those 
who  do  not,  and  that  they  see  better  at  night  and  can  read  better  by 
moonlight. 

1  "Traitg  des  Maladies  de  1'Oeil,"  1707. 


HISTORICAL  NOTES.  3 

Indeed  there  appear  so  many  advantages  in  the  strabismic  con- 
dition that  the  distinguished  author  makes  no  suggestion  for  im- 
provement. 

For  much  of  the  neglect  and  many  of  the  misconceptions  regard- 
ing the  nature  of  strabismus  in  early  times  we  may,  perhaps,  find  an 
explanation  in  the  fact  that  during  the  early  periods  of  what  is 
known  as  medical  history  it  was  unlawful  and  sacrilegious  to  make 
dissections  of  the  human  body.  This  difficulty  had,  however,  been 
in  a  great  measure  overcome  in  the  time  of  the  writer  just  quoted, 
and  indeed,  some  of  the  most  beautiful  engravings  of  dissections  of 
the  eye  and  its  muscles  are  to  be  found  in  the  works  of  the  seventeenth 
and  eighteenth  centuries. 

It  was  in  the  very  beginning  of  the  nineteenth  century  that  Tenon 
gave  to  the  world  his  descriptions  of  the  anatomy  of  the  parts  within 
the  orbit,1  which  have  remained  classic  till  the  present  time.  On  the 
other  hand,  the  fact  that  dissections  had  not  shown  any  disease  or 
appreciable  defect  of  the  muscles  toward  which  strabismic  eyes  turned, 
may  have  caused  the  withdrawal  of  attention  from  the  muscles  as  a 
direct  cause  of  the  defect  and  thus  have  delayed  the  practice  of  the 
treatment  which  was  adopted  during  the  last  half  of  the  nineteenth 
century. 

Erasmus  Darwin2  asserts  that  squinting  is  generally  owing  to 
"one  eye  being  less  perfect  than  the  other ;  on  which  account  the 
patient  endeavors  to  hide  the  worst  eye  in  the  shadow  of  the  nose 
that  his  vision  by  the  other  may  not  be  confused. 

"Calves,  which  have  an  hydatid  with  insects  inclosed  in  it  in  the 
frontal  sinus  of  one  side,  turn  toward  the  afflicted  side;  because  the 
vision  on  that  side  by  the  pressure  of  the  hydatid  becomes  less  per- 
fect .  .  .  ." 

In  regard  to  treatment  he  continues:  "If  the  squinting  has  not 
been  confirmed  by  long  habit,  and  one  eye  be  not  much  worse  than 
the  other,  a  piece  of  gauze  stretched  on  a  circle  of  whale  bone,  to 
cover  the  best  eye  in  such  a  manner  as  to  reduce  the  distinctness  of 
vision  of  this  eye  to  a  similar  degree  of  imperfection  with  the  other, 
should  be  worn  some  hours  every  day,  or  the  better  eye  should  be 
totally  darkened  by  a  tin  cup  covered  with  black  silk  for  some  hours 
dailv." 


1  Tenon:      "Memoirs   et   d'Observations   sur   1'Anatomie,  etc.,   de  1'Oeil," 
Paris,  1806. 

2Zoonomia,  1801. 


4  INTRODUCTION. 

In  more  recent  time  Eossi1  reported  his  researches  on  the  pathol- 
-ogy  and  treatment  of  strabismus  which  led  him  to  the  belief  that,  in 
strabismus,  the  orbital  cavity  "instead  of  having  the  form  of  a  right 
pyramid  as  is  natural,  has  that  of  a  pyramid  more  or  less  oblique," 
and  his  treatment  was  similar  to. that  of  zEgineta  and  Pare. 

Thus  we  have,  by  recalling  the  writings  of  representative  authors, 
sketched  an  outline  of  the  history  of  the  views  entertained  by  the 
learned  of  their  times  from  the  earliest  authoritative  writings  in 
medicine  up  to  the  era  of  an  entirely  new  departure  in  respect  to  the 
views  concerning  the  aetiology  and  treatment  of  this  defect.  It  is  easy 
to  see  that  even  up  to  the  beginning  of  the  nineteenth  century  the 
ideas  of  those  of  highest  authority  were,  in  respect  to  both  the  etiology 
and  treatment,  crude  and  confused,  and  that  they  had  scarcely  been 
modified  in  essential  respects  from  those  of  Paulus  ^Egineta  in  the 
seventh  century.  It  may  be  added  that  the  subject  of  strabismus 
during  a  period  of  many  years  preceding  the  epoch  of  which  we  are 
presently  to  speak  found  only  rarest  mention  in  the  periodical  litera- 
ture of  the  times. 

Before  entering  upon  an  account  of  the  new  era,  however,  we 
may  for  a  moment  consider  the  relations  of  two  persons,  of  most  op- 
posite character,  to  the  progress  of  events  in  this  line  of  surgical 
research. 

Rather  more  than  a  century  and  a  half  ago  an  itinerant  oculist, 
John  Taylor  by  name,  announced  in  a  book  which  he  distributed  on 
his  itineraries,  and  through  newspapers,  that  he  practiced  the  straight- 
ening of  cross  eyes  by  operation.  The  title  of  one  of  Taylor's  pam- 
phlets was,  "De  Vera  Causa  Strabismi,"2  and  he  related  the  results 
claimed  by  his  operations. 

Taylor  styled  himself  oculist  of  King  George  II  of  England. 
Elsewhere  he  styled  himself  papal  oculist,  ducal  and  court  oculist, 
with  other  high  sounding  titles. 

The  following  announcement3  of  these  operations  appeared  in 
the  Mercury  of  France,  in  June,  1737:  "Dr.  Taylor,  oculist  to  the 
King  of  Great  Britain,  has  just  arrived  in  Paris,  at  the  London 
Hotel,  Rue  Dauphine,  where  he  proposes  remaining  till  the  begin- 
ning of  July,  after  which  he  will  leave  for  Spain.  He  requests  us 


1  Mem.  Aead.  Scien.,  Turin,  T.  34.     Also  Neue  Unters.  und  Erf.  iiber  das 
Schiel,  u.  s.  v.,  Gottingen,  1841. 

2  Paris,  Lisbonne,  1738. 

•Walton:  "Diseases  of  the  Eye,"  p.  366. 


HISTORICAL  NOTES.  5 

to  publish  the  discoveries  he  has  made  of  straightening  squint  eyes 
by  a  slight  and  almost  painless  operation,  and  without  fear  of  acci- 
dent." 

Xearly  twenty  years  later,  in  1756,  Heuerman,  a  German  sur- 
geon, published  a  work  entitled  "Abhandlung  der  neusten  Chirur- 
gische  Operationem"  in  which  the  author  thus  mentions  Taylor's 
claims1 : — 

"Taylor  has  also  proposed  to  cure  squinting  by  the  division  of 
the  tendon  of  the  superior  oblique  muscle  of  the  eye.  But  this  de- 
formity is  not,  in  every  case,  produced  by  the  contraction  of  this 
muscle;  and  moreover  the  inferior  oblique  muscle  is  apt  to  draw  the 
eyeball  in  the  opposite  direction  when  the  superior  one  is  divided, 
thus  giving  rise  to  a  new  sort  of  squinting.  In  addition  to  this,  the 
recti  muscles,  the  contraction  of  which  often  occasions  squinting,  can- 
not be  easily  cut  across,  in  consequence  of  their  situation.  We  thus 
see  that  the  operation  performed  by  Taylor  can  only  be  of  temporary 
benefit;  and  we  cannot  expect  that  patients  will  submit  to  it,  seeing 
that  it  is  attended  with  a  good  deal  of  pain,  and  its  results  are  so 
uncertain.'" 

Lucien  Boyer2  quotes  from,  a  long  forgotten  address  by  LeCat 
at  the  Academic  des  Sciences,  Belles  Lettres  et  Arts,  of  Bouen,  the 
following  narrative. 

The  writer,  after  noticing  the  danger  of  charlatanism  which 
should  be  met  not  only  by  the  medical  profession  but  by  the  laws, 
illustrates  his  theme  by  relating  that  he  had  seen  Dr.  T.,  whose  bear- 
ing and  accessories  he  thus  describes: — 

"This  refined  and  amiable  man  came  to  Eouen  the  ,  and 

within  a  few  days  became  the  object  of  general  admiration.  He  had 
an  arsenal  of  superb  instruments  and  handled  them  with  great  dex- 
terity. He  showed  portfolios  filled  with  authentic  and  highly  com- 
mendatory credentials.  The  door  to  his  hotel  was  guarded  by  soldiers 
and  it  was  necessary  for  one  to  have  an  introduction  in  order  to  visit 
him.  His  operations  were  done  in  the  midst  of  a  brilliant  circle  of 
select  persons. 

"The  great  operation,  the  most  marvelous  of  all,  was  that  by 
which  he  proposed  to  straighten  squinting  eyes.  His  method  was  as 
follows:  With  a  needle  of  silk  he  caught  a  portion  of  the  conjunctiva 
of  the  squinting  eye  at  the  inferior  part  of  the  globe,  and  having  made 


1  Medieo-Chirurgical  Review,  1842,  p.  194. 

3  "Recherches  sur  1'Operation  du  Strabisme,"  1842,  p.  38. 


6  INTRODUCTION. 

a  loop  of  this  silk  be  used  it  to  draw  toward  him  that  portion  of  the 
conjunctiva  which  it  included,  which  he  cut  with  the  scissors;  then 
he  applied  a  plaster  to  the  sound  eye;  the  squinting  eye  at  once 
righted  itself  and  every  one  cried  out,  'a  miracle/ 

"I  availed  myself  of  the  freedom  which  he  accorded  me  to  in- 
quire the  motive  for  an  operation  which  appeared  to  me  to  be  abso- 
lutely useless,  not  to  say  dangerous.  He  replied  that  an  eye  only 
squinted  because  the  equilibrium  between  its  muscles  was  destroyed, 
and  that  to  re-establish  this  equilibrium  it  was  only  necessary  to 
weaken  the  muscle  which  dominated  the  others  and  that  this  is  what 
he  did  in  cutting  one  of  the  nerve  filaments  which  was  distributed  to 
this  too  powerful  muscle." 

Whatever  may  have  been  Taylor's  method,  whether  he  divided 
the  superior  oblique  as  Heuerman  asserts  or  the  inferior  oblique  as 
others  state,  whether  the  brilliant  and  clever  man  described  by  LeCat 
really  only  cut  a  fold  of  conjunctiva,  it  is  certain  that  Taylor's  work 
had  no  influence  in  introducing  the  surgical  method  of  treatment  to 
the  world.  If  he  divided  one  of  the  oblique  muscles  as  he  was  sup- 
posed to  do,  he  did  not  correct  the  squint,  and  if  he  simply  divided 
the  conjunctiva  and  some  supposed  nervous  filaments  which  were  as- 
sumed to  supply  a  muscle,  he  still  did  not  cure  the  squinting.  There 
remain  two  possibilities :  first,  that  the  secret  of  the  whole  operation 
lay  in  the  fact  stated  by  LeCat:  he  covered  the  sound  eye  with  plas- 
ter; the  squinting  eye  became  straight  and  the  people  cried  "'a, 
miracle."  Second,  and  it  is  much  more  probable,  however,  that  he 
cut  the  internal  rectus,  but  that  he  did  not  confide  too  much  in  his 
not  well-informed  critics. 

The  story  of  Taylor  is  interesting  for  what  it  suggests,  first  in 
in  regard  to  himself,  and  second  in  regard  to  the  medical  profession. 
If  Taylor  really  corrected  squint  by  an  operation  on  a  lateral  muscle, 
he  would  have  acquired  enduring  fame  had  his  discovery  been  made 
permanently  known  by  an  exact  and  honest  description  of  his  meth- 
ods. If  he  carried  the  idea  tha.t  he  operated  upon  an  oblique,  when 
he  in  reality  cut  an  internal  rectus,  he  committed  suicide  for  his 
reputation.  If,  on  the  other  hand,  he  really  cut  an  oblique,  he  made 
no  cure  and  therefore  has  no  claim  to  be  regarded  as  a  pioneer  in  the 
surgery  of  strabismus. 

There  is  a  view  of  the  whole  subject,  however,  which  is  not  to 
be  lost  sight  of.  That  Taylor  was  a  man  of  learning  is  not  to  be 
doubted.  He  had  studied  at  Leyden  and  at  other  universities.  That 


HISTORICAL  NOTES.  7 

he  was  a  charlatan  may  also  be  true,  but  the  age  was  an  age  of  char- 
latanism. His  works  which  remain  to  us  show  that,  breaking  away 
from  the  theories  of  Maitre-Jan  and  of  all  his  predecessors,,  he  had 
correctly  appreciated  the  cause  of  strabismus.  That  a  man  of  un- 
doubted ability  and  who  correctly  interpreted  the  phenomena  of 
squinting  should  have  resorted  to  a  cheap  trick  which  must  have  been 
exposed  without  delay,  while  he  absolutely  failed  to  practice  the  prin- 
ciple which  he  certainly  understood,  seems  incredible. 

That  no  published  description  is  known  or  seems  to  have  been 
known  is  certain.  But  it  is  too  true  that  in  medical,  as  well  as  in 
other  fields  of  science,  a  truth  not  acceptable  or  not  understood  by 
the  contemporaries  of  the  discoverer  is  either  distorted  in  transmis- 
sion or  altogether  lost  to  the  world  by  neglect.  The  fact  that  we 
know  of  no  detailed  description  is  not  evidence  that  there  was  none, 
and  the  description  of  the  distinguished  LeCat  would  not  be  further 
from  a  true  comprehension  of  the  actual  facts,  in  case  Taylor  really 
performed  a  tenotomy  of  the  internus,  than  is  shown  by  distinguished 
authorities  of  the  present  time  when  they  attempt  the  description  of 
some  procedure  with  which  they  are  not  fully  in  sympathy. 

The  history  of  Taylor's  claims  is  therefore  interesting  in  its 
bearings  upon  some  characteristics  of  the  medical  profession. 

The  claim  that  strabismus  could  be  corrected  by  relaxing  "the 
too  dominant  tendon"  was  not  only  rational,  but  would  seem  to  be 
one  which  should  have  been  seized  upon  by  the  surgical  mind.  Doc- 
tors are,  however,  like  other  men,  and  the  fact  that  Taylor  was  an 
itinerant  and  therefore  assumed  to  be  a  man  of  no  scientific  authority, 
instead  of  setting  men  to  think  in  the  right  way,  prompted  them  only 
to  oppose  the  idea  as  unscientific. 

Let  us  now  turn  to  a  person  of  widely  different  character. 

The  mention  of  the  name  of  Charles  Bell  suggests  at  once  to 
the  mind  a  series  of  researches  in  respect  to  the  anatomy  and  phys- 
iology of  the  nerves  which  were  in  the  highest:  degree  epoch-making. 
It  is  needless  to  mention  any  of  these  remarkable  inquiries  and  dis- 
coveries save  a  single  series  of  observations  relating  to  the  movements 
of  the  eyes.1 

In  his  experimental  inquiries  Sir  Charles  divided  (1)  the  supe- 
rior rectus  in  a  rabbit  and  felt  some  disappointment  on  observing  the 


1  Read  before  the  Royal  Society,  March  20.  1823.    Published  as  a  chapter 
of  "The  Nervous  System  of  the  Human  Body,"  1830. 


g  INTRODUCTION. 

eye  remain  stationary.  Shortly  afterward  on  looking  at  the  animal 
he  saw  "the  pupil  depressed."  The  animal  could  not  raise  the  eye. 

(2)  On  opening  the  eyelids  and  irritating  the  eye  of  which  the 
superior  rectus  had  been  divided,  the  eye  was  turned  up ;    showing, 
as  the  experimenter  believed,  that  though  voluntary  motion  was  lost, 
involuntary  motion  remained  by  the  influence  of  the  obliques. 

(3)  Wishing  to  ascertain  if  the  oblique  muscles  contract  to  force 
the  eyeball  laterally  toward  the  nose,  he  put  a  fine  thread  around  the 
tendon  of  the  superior  oblique  muscle  of  a  rabbit  and  appended  a  glass 
bead  to  it  of  a  weight  to  draw  out  the  tendon  a  little.     On  touching 
the  eye  with  a  feather  the  bead  was  drawn  up. 

Experiments  made  on  the  dead  body  had  shown  him  that  the 
action  of  the  superior  oblique  muscle  is  to  turn  the  pupil  downward 
and  outward  and  that  the  inferior  oblique  "reverses  this  action  of 
the  eye."  He  concluded  from  the  bead  experiment  that  the  com- 
bined action  of  the  two  oblique  muscles  is  to  draw  the  eye  to  the  nose. 

(4)  He  cut  through  the  tendon  of  the  superior  oblique  muscle 
of  a  monkey.      He  saw  no  change  in  the  appearance  or  movements 
of  the  eye. 

(5)  A   similar  result  followed  section  of  the  inferior  oblique. 
From  these  experiments  he  considered  it  proved  that  division 

of  the  oblique  muscle  does  not  affect  vohmtarily  motions  by  which 
the  eye  is  directed  to  objects,  and  that  division  of  the  recti  does  not 
prevent  involuntary  motions.1 

In  the  experiment  on  the  superior  rectus  muscle  the  learned 
investigator  saw  the  eye  dropped  from  its  normal  direction  yet  still 
able  to  move  upward.  We  are  led  to  wonder  Avhy  so  brilliant  an 
anatomist  and  physiologist  could  have  turned  away  from  the  evident 
teaching  of  his  own  experiment.  We  have  an  instance  of  one  who 
has  placed  before  himself  all  the  elements  of  a  grand  discovery,  but 
who  turns  away  from  the  positive  to  the  negative  teachings  of  the 
conditions  which  he  has  induced.  Had  an  anatomist  desired  to  prove 
to  himself  and  others  that  squinting  could  not  be  cured  by  section 
of  the  obliques  these  experiments  would  have  been  satisfactory  to 
him. 

It  not  infrequently  happens  that  the  state  of  mind  in  which  an 
inquiry  is  entered  upon  controls  the  result  whatever  may  have  been 
the  facts  evolved  by  the  inquiry. 


1  In  the  summary  of  these  experiments  the  words  of  the  author  have  been 
employed  as  far  as  it  has  been  found  convenient. 


HISTORICAL  NOTES.  9 

We  now  enter  upon  the  period  of  actual  discover}'  of  the  surgical 
treatment  of  strabismus. 

The  process  now  known  as  the  operation  for  strabismus  was  sug- 
gested and  described  by  Stromeyer,  professor  of  surgery  in  the  Uni- 
versity of  Erlangen,  in  1838,  and  the  first  authenticated  operation 
was  executed  on  the  26th  of  October,  1839,  by  Dieffenbach,  in  Berlin. 

A  full  appreciation  of  these  two  stages  in  the  discovery  of  what 
was  then  called  ocular  myotomy  requires  some  knowledge  of  the  con- 
temporary tendencies  of  surgery.  The  time  was  emphatically  a  period 
of  myotomies.  The  two  names  which  figure  most  prominently  in  the 
introduction  of  the  strabismus  operation  are  also  those  of  two  among 
the  most  distinguished  myotomists  of  the  time.  Stromeyer,  whose 
first  subcutaneous  tenotomy  of  the  tendo-achillis,  in  1831,  had  fallen 
far  short  of  success,  had  yielded  to  no  discouragements,  but  had  ex- 
tended the  process  to  all  parts  of  the  human  body,  and  Dieffenbach 
claimed  to  have  myotomized  nearly  forty  different  muscles,  some  of 
them  a  great  number  of  times. 

M.  Jules  Guerin,  "le  Grande  Myotomiste"  of  the  Orthopedic 
Institute  of  Paris,  whose  friends  claimed  for  him  a  large  measure 
of  credit  for  the  introduction  of  the  strabismus  operation,  in  an  arti- 
cle in  the  Gazette  Medicale,  gave  a  list  of  the  parts  which  he  had 
divided  by  the  method  of  subcutaneous  incision  which  looks  almost 
like  a  catalogue  of  the  muscles  of  the  trunk,  neck,  upper  and  lower 
extremities. 

Such  was  the  drift  of  surgical  thought  and  action  when,  in  1838, 
there  was  published,  at  Hanover,  a  treatise  on  "Subcutaneous  Ortho- 
pedics," by  Prof.  L.  Stromeyer,1  in  which  he  showed  that  strabismus 
might  be  regarded  as  a  vicious  contraction  of  the  eye  muscles  and 
that  the  same  treatment  might  be  applied  to  it  as  to  club-foot.  He 
fully  described  the  procedure  by  which  the  operation  could  be  done 
and  reported  the  effect  of  many  tenotomies  done  by  his  method  on  the 
dead  subject.  For  a  time  no  attention  seems  to  have  been  attracted 
to  Stromeyer's  views  of  squint,  but  at  length  it  was  noised  abroad  in 
all  lands  that  Dieffenbach,  of  Berlin,  had  applied  the  method  of 
Stromeyer  to  the  living  subject. 

In  February,  1840,  Dieffenbach  communicated  his  discovery  to 
the  French  Academy  of  Sciences,  which  at  the  time  was  offering  the 
Moynton  prize  for  a  notable  discovery  in  medicine  and  surgery,  but 


1  Beitrlige  zur  Operativen  Orthopedic  u.  s.  v.,  Hanover,  1838 


10  INTRODUCTION. 

to  the  commission  having  the  matter  in  charge  the  claim  of  the  Berlin 
surgeon  appeared  so  improbable  that  it  was  regarded  rather  as  a 
burlesque  than  a  serious  claim  for  the  award.  Still  later  Dieffenbaeh 
forwarded  a  second  communication  in  which  he  not  only  reported 
many  cases,  but  gave  the  minute  details  of  the  process  and  of  the 
progress  of  the  new  operation. 

From  this  time  the  medical  journals  in  which  the  mention  of 
strabismus  had  been  only  at  intervals  of  years,  teemed  with  articles  on 
the  now  interesting  topic. 

The  commission  of  the  Academy  of  Sciences  could  now  no  longer 
withhold  its  recognition  of  the  great  value  of  the  discovery  and  in 
awarding  the  prize  the  commission  reported :  "The  commission  has 
the  honor  to  propose  to  the  Academy  to  award  Messrs.  Stromeyer  and 
Dieffenbach  a  prize  of  six  thousand  francs  to  be  divided  between  them. 
They  awarded  it  to  M.  Stromeyer  for  having  first  conceived  and  exe- 
cuted the  operation  of  strabismus  upon  cadavers,  and  to  M.  Dieffen- 
bach for  having  first  successfully  practiced  the  operation  upon  the 
living  man."1 

It  will  be  interesting  and  profitable  to  inquire  into  the  methods 
and  principles  involved  in  these  early  operations,  and  to  trace  any 
modifications  which  may  have  resulted  from  larger  experience  and 
fuller  examination  of  the  subject. 

Dieffenbach's  first  operation,  described  in  Medicinische  Zeitung, 
November,  1839,  omitting  the  details  of  fixation  of  the  eye  and  the 
lids,  details  not  essential  to  the  method  of  operating,  consisted  in 
"cutting  through  the  conjunctiva  and  separating  the  connective  tis- 
sue," then  "dividing  the  internal  rectus  muscle,  using  scissors,  close 
to  its  insertion.  The  eve  was  immediatelv  drawn  outward  by  the 

«/  «/  «/ 

external  rectus,  as  if  it  had  received  an  electric  shock;  and  in  an- 
other instant  became  straight "• 

In  his  second  case  "the  operation  was  performed  as  in  the  last 
case,  the  conjunctiva  being  cut  through  and  the  sclerotic  laid  bare  to 
the  extent  of  four  lines,  in  order  to  bring  the  muscle  into  view,  which 
was  cut  with  a  curved  scissors  as  before." 

Mr.  P.  Bennett  Lucas,  one  of  the  earliest  of  English  surgeons  to 
perform  the  operation  of  Dieffenbach,  describes  his  operation  in  the 
Provincial  Medical  and  Surgical  Journal,  October,  1840.  After 
dividing  the  conjunctiva  and  the  connective  tissue  to  the  desired 


1  Space  does  not  permit  of  mention  of  tlie  many  claims  which  were  set  up 
for  priority  as  soon  as  the  operation  became  a  success. 


HISTORICAL  NOTES.  H 

extent,  "the  blunt  hook  heing  inserted  beneath  the  muscle,  the  oper- 
ator transfers  it  to  the  left  hand,  and  having  brought  the  tendon  into 
view,  he  divides  it  with  a  sharp-pointed  pair  of  scissors  as  close  to  its 
insertion  as  is  compatible  with  the  safety  of  the  sclerotic." 

Mr.  Liston  also,  in  the  London  Lancet,  1840,  says:  "With  a 
little  dissection  the  muscle  is  seen  just  as  it  ends  in  its  tendon,  and 
with  a  pair  of  scissors  it  is  cut  across  close  to  its  insertion  into  the 
sclerotic." 

It  thus  appears  that  in  the  earliest  history  of  the  operation  it 
consisted  essentially  of  a  division  of  the  conjunctiva  over  the  insertion 
of  the  tendon,  usually  about  a  third  of  an  inch  in  extent,  introducing 
a  probe  or  blunt  hook  beneath  the  tendon  and  dividing  the  latter  with 
a  pair  of  scissors  close  to  the  sclerotic. 

The  cure  of  strabismus  soon  became  a  show  operation,  and  while 
the  political  press  teemed  with  columns  of  sensational  descriptions 
of  the  operation,  surgeons  plunged  with  a  will  into  a  system  of  char- 
latanism and  surrounded  themselves  with  admiring  crowds  to  witness 
the  miraculous  changes  which  their  art  could  produce.  As  is  usual 
when  surgery  is  done  for  popular  applause,  the  question  of  the  best 
method  for  obtaining  best  effects  became  an  entirely  secondary  one 
and  tenotomies  soon  gave  place  to  myotomies.  Dieffenbach  himself 
led  in  the  degradation  of  his  operation  and  asserted  that  the  further 
back  the  muscle  is  divided  the  more  effectually  will  the  more  pro- 
nounced cases  of  strabismus  be  relieved.  "If,"  he  says,1  "the  con- 
junctiva be  divided  over  a  greater  arc  and  toward  the  back  of  the 
globe,  if  the  cellular  tissue  be  extensively  separated  and  the  muscle 
be  detached  far  back  and  divided  at  its  middle,  then  the  eye,  even 
in  cases  in  which  the  whole  cornea  was  hidden  in  the  internal  angle, 
stands  quite  straight  after  the  operation." 

The  practice  of  dividing  the  tendon  at  some  distance  from  the 
sclera  was  continued  for  a  number  of  years.  The  text  and  illustration 
descriptive  of  the  operation  in  the  edition  of  1854,  of  McKenzie's 
"Treatise  on  the  Eye,"  shows  the  section  of  the  tendon  several  lines 
removed  from  the  sclera.  That  a  reaction  against  the  operation  set 
in  was  but  the  legitimate  result  of  these  extravagant  destructions  of 
the  rotating  powers  of  the  eyes. 

It  was  in  this  stage  of  repudiation  by  a  large  proportion  of  con- 
servative surgeons  that  the  great  authority  of  von  Graefe  called  his 


1  Casper's    "\Vochenschrift,"    July,    1840,    quoted    in    Braithwaite's    "Re- 
trospect." 


12  INTRODUCTION. 

colleagues  to  a  return  to  a  more  conservative  policy.  He  advised  that 
the  incision  in  the  conjunctiva  be  made  near  the  cornea,  that  the 
section  of  the  tendon  be  made  close  to  the  sclera,  and  that  in  all  but 
cases  in  which  extensive  effects  were  required,  a  suture  should  be 
introduced  in  the  conjunctiva!  wound.  In  pronounced  cases  he  divided 
the  whole  of  the  tendon  and  all  the  surrounding  connective  tissue  with 
the  capsule;  in  less  pronounced  cases  the  connective  tissue  was  less 
completely  divided,  and  in  slight  cases  he  severed  the  tendon  except 
the  upper  or  the  lower  border  of  a  lateral  muscle  or  an  inner  or  an 
outer  border  of  a  vertically  acting  muscle,  a  process  which  he  termed 
partial  tenotomy,  and  which  must  of  necessity  have  been  accompanied 
by  a  tilt  of  the  globe,  a  condition  as  little  to  be  commended  as  the 
myotomies  of  his  predecessors.  In  all  essential  features  this  operation 
became  the  standard  operation  in  all  countries,  and  with  slight  modi- 
fications representing  the  fancy  of  individual  operators  has  remained 
the  classic  operation  in  all  the  text-books  to  the  present  time. 

A  moment's  reflection  will  show  that  the  operation  as  laid  down 
by  von  Graefe  and  repeated  in  the  current  text-books  is  that  executed 
and  described  by  Dieffenbach,  Lucas,  Liston,  and  other  pioneers  in  the 
operation,  and  that  the  real  difference  between  the  modern  procedure 
and  that  of  the  earliest  operators  consists  in  the  details  of  holding 
the  lids  apart  and  of  fixing  the  eye. 

It  will  not  be  without  interest  to  compare  the  text  and  illustrative 
figure  referring  to  the  operation  in  the  text-book  of  Desmarres,  1847, 
and  the  corresponding  text  and  illustrations  from  the  more  modern 
text-books. 

It  will  not  be  out  of  place  here  to  inquire  into  the  exact  meaning 
of  one  expression  which  characterizes  the  rule  given  by  the  early 
operators  and  that  given  by  von  Graefe.  We  are  told  by  both  author- 
ities to  perform  the  section  of  the  tendon  as  nearly  as  possible  to  the 
sclera.  And  the  question  arises  as  to  the  precise  meaning  of  the. 
phrases  in  which  this  direction  is  given. 

If  we  are  to  accept  the  illustrative  figures  which  accompany  the 
modern  text-books  as  representing  the  operation,  if  we  are  to  accept 
the  ordinary  practice  of  the  great  majority  of  surgeons  who  follow  the 
teachings  of  von  Graefe,  and  especially  if  we  consider  the  instruments 
which  are  generally  figured  and  used,  it  becomes  evident  that  these 
phrases  are  intended  to  teach  that  the  section  is  to  be  made  in  the 
near  vicinity  of  the  sclera,  but  that  a  dissection  of  the  tendon  at  its 
very  union  could  not  be  intended.  Such  a  dissection  would  be  almost 


HISTORICAL  NOTES.  13 

out  of  the  question  with  the  instruments  employed  by  von  Graefe  and 
which  are  still  quite  in  vogue. 

As  a  matter  of  fact  in  these  operations,  done  according  to  the 
prevailing  method,  the  section  is  made  at  a  few  millimeters  from  the 
globe. 

From  the  aetiological  point  of  view  there  has  been,  during  the 
half-century  and  more  since  the  introduction  of  the  surgical  treat- 
ment of  squint,  omitting  for  the  present  any  reference  to  any  sug- 
gestions of  my  own,  one  notable  doctrine,  that  of  Donders,  which  he 
formulated  as  follows : — 

1.  Strabismus  convergens  almost  always  depends  upon  hyper- 
metropia. 

2.  Strabismus  divergens  is  usually  the  result  of  myopia. 

These  propositions  were  at  once  universally  accepted,  yet  there 
is  to-day  quite  sufficient  reason  for  revising  the  judgment  of  the  pro- 
fession, for  there  is  adequate  ground  for  saying  that  the  doctrine  of 
Donders  rests  upon  neither  theoretical  nor  practical  grounds.  With 
the  exception  of  the  doctrine  of  Donders,  the  accepted  views  respect- 
ing the  aetiology  of  strabismus  have  in  the  profession  at  large  under- 
gone slight  change  during  the  half-century. 

In  the  meantime  if  some  views  which  I  have  myself  advanced  are 
at  least  new,  it  is  not  my  purpose  to  discuss  them  in  this  connection, 
beyond  saying  that  by  the  aid  of  the  tropometer  and  the  clinoscope 
we  may  now  arrive  at  the  conditions  underlying  the  great  majority  of 
cases  of  squint  with  so  much  certainty  that  we  are  able  to  relieve  the 
defect  without  inducing  another,  as  was  the  universal  rule  under  the 
former  regime. 

In  the  half-century,  much  careful  work  has  added  to  the  stock 
of  precise  anatomical  knowledge  of  the  muscles  of  the  eyes  and  their 
insertions.  Observations  from  a  physiological  standpoint  have  also 
furnished  material  not  accessible  a  half  century  since  which  permits 
of  more  correct  conclusions. 

The  different  varieties  of  concomitant  strabismus  were  described 
in  the  years  immediately  following  the  introduction  of  the  operation 
for  tenotomy  of  the  recti  muscles  much  as  they  are  to-day  in  the  best 
text-books. 


14  INTRODUCTION. 

SECOND  PERIOD — HETEROPHORIA. 
ANOMALIES  OF  THE  EYE  MUSCLES  LESS  THAN  STRABISMUS. 

Leaving  for  the  present  the  subject  of  strabismus,  we  may  trace 
the  history  of  the  progress  of  knowledge  in  respect  to  those  anom- 
alies of  the  eye  muscles  less  conspicuous,  but  as  experience  is  proving, 
no  less  important,  which  are  at  the  present  time  known  under  the 
generic  term  heteroplioria.  To  these  anomalies  may  be  added  those 
of  declination  and  those  others  which  may  be  investigated  by  the 
tropometer. 

While  it  is  true  that  the  names  of  some  of  those  who  have  been 
identified  with  the  progress  of  modern  ophthalmology  have  been  also 
identified  with  a  single  aspect  of  this  special  branch  of  the  subject  of 
anomalies  now  to  be  considered,  it  is  also  true  that  previously  to  my 
own  contributions,  not  only  had  attention  been  directed  exclusively 
to  this  single  aspect,  but  even  in  respect  to  that  no  clear  and  definite 
views  were  entertained. 

In  1857  von  Graefe  called  attention  to  a  form  of  strabismus,  less 
evident  to  the  general  observer  than  the  recognized  form,  which  he 
termed  latent  strabismus  or  insufficiency  of  the  internal  recti.  which 
"was  characterized  by  an  ability  to  hold  the  images  of  the  two  eyes  in 
union  while  the  gaze  was  directed  at  distant  objects,  but  by  deviation 
of  one  eye  outward  when  a  near  object  was  looked  at.  Thus,  if  a 
pencil  were  held  in  front  of  the  subject  of  this  defect  and  the  eyes 
were  directed  toward  it,  the  axis  of  each  eye  appeared  to  be  directed 
to  the  object  until  it  approached  as  near  as  the  reading  distance,  when 
one  eye  deviated  outward.  This  condition  he  found  mostly  in  cases 
of  myopia  of  high  degree  and,  as  just  mentioned,  he  called  it  "In- 
sufficiency of  the  Internal  Eecti  Muscles."1 

There  is  no  reason  to  suppose  that  von  Graefe  designed  by  this 
term  to  intimate  that  the  internal  recti  were  weak ;  that  interpretation 
was  the  result  of  an  imperfect  understanding  on  the  part  of  some  who 
did  not  fully  comprehend  the  meaning  of  von  Graefe's  language.  Yon 
Graefe's  meaning  was,  that  in  these  cases  of  myopia,  where  the  object 
must  be  held  close  to  the  eyes  and  the  tendency  of  the  lines  of  sight  was 


1  "Another  source  of  asthenopia  is  quite  independent  of  the  accommodative 
function,  and  lies  in  the  contractile  ability  of  the  inner  eye  muscles.  I  have 
several  years  since  spoken  of  this  form  as  'Insufficiency  of  the  Internal  Recti 
Muscles,'"  etc.  V.  Graefe,  Arch.  f.  Oph.  viii,  ii,  315,  1861. 


HISTORICAL  NOTES.  15 

outward,  greater  than  normal  tension  was  required  of  the  intern!  and 
they  were  insufficient  for  the  unusual  task.  This  is  the  meaning  which 
runs  through  all  his  writings  on  the  subject.  He  speaks  of  the  con- 
traction excess  required  to  induce  the  proper  convergence,  not  the 
contraction  weakness.  True,  he  mentions  the  general  muscular  weak- 
ness attending  convalescence  from  severe  illness,  but  he  includes  such 
cases  in  a  class  by  themselves.  They  are  temporary  cases  which  result 
in  "spontaneous  recovery." 

This  condition  of  insufficiency  of  the  internal  recti  he  regarded 
as  a  cause  of  asthenopia  equal  to  hypermetropia  and  he  proposed 
methods  for  examinations  and  treatment.  In  examining  he  used  the 
method  already  mentioned,  the  fixing  of  the  gaze  upon  a  pencil  as  it 
was  made  to  approach  from  a  distance. 

For  more  accurate  measurement  of  the  deviation  a  prism  was 
held  with,  its  edge  up  before  one  eye  while  the  patient  looked  at  a  card 
held  a  foot  or  more  in  front  of  the  eyes  and  on  which  was  drawn  a 
vertical  line  with  a  dot  in  the  middle.  If  this  line  separated  and  the 
dots  separated  heteronymously  there  was  insufficiency  of  the  internal 
recti  to  the  extent  of  the  value  of  the  prism  which,  held  horizontally, 
would  throw  the  two  dots  on  a  single  line. 

Von  Graefe  employed  spectacles  of  prisms  with  their  bases  in 
for  the  relief  of  this  condition,  but  he  preferred  the  more  radical 
method  of  dividing  the  external  rectus  of  the  deviating  eye  or,  more 
rarely,  of  both  externi,  to  the  extent  that  the  dots  would  continue  on 
the  one  vertical  line.  He  was  willing  to  sacrifice  single  vision  at  the 
distance,  causing  homonymous  diplopia  by  his  operation,  for  since 
these  people  were  mostly  myopic,  the  homonymous  double  images 
would,  in  his  estimation,  cause  little  inconvenience,  while  the  object 
sought,  the  ability  to  converge  at  near  points,  would  be  accomplished.1 

This  was  practically  the  whole  doctrine  of  "insufficiency"  up  to 
the  time  when  more  especial  attention  was  called  to  these  conditions  by 
myself.  In  all  the  text-books  and  in  all  the  current  literature,  so  far 
as  the  subject  received  any  notice,  muscular  asthenopia  was  "insuffi- 
ciency of  the  interni." 

It  is  true  that  there  were  a  few  references  to  "insufficiency  of  the 
externi."  It  requires  but  a  glance  at  these  references  to  see  that  they 
related  generally,  if  not  in  every  instance,  to  moderate  cases  of  con- 
verging strabismus.  To  this  we  shall  presently  return. 

1  Loc.  cit.,  p.  348. 


16  INTRODUCTION. 

Von  Graefe  left  to  the  world,  among  his  richest  contributions  to 
the  literature  of  science,  extensive  memoirs  upon  subjects  connected 
with  the  ocular  muscles,  replete  with  the  evidences  of  his  great  pow- 
ers of  observation  and  of  his  remarkable  genius. 

His  observations  were  those  of  a  pioneer.  They  were  not  com- 
plete and  the  interpretations  conformed  to  the  modes  of  thought  of 
his  time.  His  conclusions  were  influenced  by  his  environments. 

To  return  to  the  single  phase  of  the  conditions  now  known  as 
heterophoria  to  which  his  observations  were  confined,  it  may  be  said 
that  even  that  phase  in  its  broader  signification  scarcely,  if  at  all, 
occupied  his  attention. 

Yon  Graefe  regarded  the  ability  to  direct  the  axes  of  the  two 
eyes  to  the  same  point  at  the  visual  distance  of  reading,  especially 
of  myopic  eyes,  without  excessive  effort,  as  a  practical  standard  of 
"equilibrium."  He  taught  that  this  should  be  gained  even  at  the 
expense  of  very  great  loss  of  equilibrium  at  greater  distances. 

Xo  such  standard  as  he  assumed  could  be  now  accepted.  Equi- 
librium does  not  exist  when  the  power  of  fusion  has  been  gained  at 
one  point  at  the  expense  of  difficulty,  or  impossibility,  of  fusion  at 
another.  The  doctrine  that  equilibrium  must  be  attained  by  inducing 
fusion  at  all  distances  equally  and  with  no  abnormal  effort  was  first 
insisted  upon  by  myself  and  has  now  become,  at  least  in  America,  uni- 
versally accepted. 

In  order  to  make  this  retrospective  view  more  effective  it  will  be 
of  interest  here  to  reproduce  the  views  which  were  standard  when  my 
own  contributions  to  the  subject  commenced. 

Von  Graefe,  as  has  been  observed,  performed  his  operations  for 
"insufficiency  of  the  internal  recti"  entirely  in  the  interest  of  uniting 
the  visual  lines  at  the  near  point,  generally  of  extremely  myopic  peo- 
ple. The  near  point  was  in  such  cases  extremely  near.  In  his  treatise 
on  "Asthenopia,"  he  says1 : — 

"As  point  of  departure  (for  tenotomy  of  the  externus)  we  must 
choose  according  to  the  reading  distance  of  the  subject.  ...  If 
we  should  do  a  little  too  much  it  would  not  cause,  at  the  near  point, 
the  least  trouble.  Strabismus  convergens  could  only  occur  if  we  have 
exceeded  the  measure  of  the  total  abduction.  .  .  .  There  will  then 
become  necessary  at  the  distance  a  tension  of  the  externi.  This  in 
itself  is,  fortunately  for  the  tenotomy,  of  no  consequence,  as  for  the 
act  of  vision  at  the  distance  the  same  results  from  continuous  strain 

fiir  Ophthal.,  viii,  2,  349. 


HISTORICAL  NOTES.  17 

do  not  occur.  Against  this,  however,  occurs  a  real  trouble.  If,  in  the 
main,  the  power  of  the  externi  is  no  longer  sufficient  for  fixation  at 
the  distance,  strabismus  convergens  with  homonymous  diplopia  is  the 
result.  When,  in  brief,  will  this  occur?  Necessarily,  if  the  definite 
effect  of  the  tenotomy  does  not  correspond  to  the  extremest  abduc- 
tion for  the  distance.  We  therefore  find  the  measure  for  the  tenotomy 
by  ascertaining  the  strongest  prism  which  can  be  overcome  by  diver- 
gence for  the  distance.  The  linear  deflection  which  corresponds  to  the 
prism  we  can  remove  without  harm  in  order  to  take  from  the  interni 
at  the  near  as  much  work  as  possible. 

"After  such  an  adjusted  tenotomy,  binocular  fixation  for  the 
distance  takes  place  with  the  greatest  strain  for  the  externi.  \Vhat  is 
then  required  of  the  externi  for  the  distance  favors  the  interni  at  the 
near  point." 

Von  Graefe  often  operated  in  this  way,  causing  15°  or  20°  ho- 
monymous diplopia  at  distance  in  the  hope  that  at  some  time  the  an- 
noyance from  the  double  images  might  disappear.  Further  on,  in 
illustrating  the  grades  of  "insufficiency"  and  the  treatment,  von  Graefe 
says : — 

"Let  a  second  patient  have,  at  the  near  point,  insufficiency 
(prism)  1G°,  at  the  distance  (v.  Graefe  regarded  three  meters,  six 
meters,  etc.,  indifferently  as  distance),  insufficiency  6°  with  abduc- 
tion (prism)  16°.  We  can  take  from  him  by  tenotomy  the  full  insuffi- 
ciency for  the  near  as  that  is  equal  to  the  abduction  for  the  distance; 
thus  he  will  now  be  just  able  to  fix  for  the  distance  though  with  the 
greatest  possible  strain  of  his  abducting  power,  to  which,  as  we  have 
already  found.,  there  is  no  objection." 

I  have  quoted  at  some  length  the  words  of  the  master  in  order 
to  show  the  meaning  of  his  term  "insufficiency  of  the  interni"  and  to 
throw  light  on  a  question  which  will  presently  arise,  whether  the  fact 
of  the  existence  of  an  opposite  condition  had  in  his  mind  any  impor- 
tance. 

It  will  be  seen  that  "insufficiency"  was  exclusively  confined  to 
the  condition  of  difficulty  in  convergence  at  very  near  points  and  that 
any  other  so-called  insufficiency  was  of  no  account.  A  condition 
barely  short  of  converging  strabismus  was  entirely  satisfactory  and 
one  of  slight  converging  strabismus  not  especially  objectionable  and 
what  objection  might  exist  was  attributable,  not  to  the  strain,  but  to 
the  annoyance  of  diplopia. 

The  "Insufficiency  of  the  Interni"  of  von  Graefe  was  the  condi- 


18  INTRODUCTION. 

tion  of  its  class  recognized  in  the  text-books  at  the  time  that  attention 
was  called  by  myself  to  the  imperfection  of  the  doctrine. 

Soelberg  Wells1  devoted  a  section  to  the  discussion  of  "Muscular 
Asthenopia  (insufficiency  of  the  interni)."  His  tests  for  the  affec- 
tion were  made  at  the  near  point.  In  determining  abduction  and 
adduction  he  removed  the  object  to  a  distance  of  from  6  to  10  feet. 

Galezowski2  discussed  "latent  divergent  strabismus/'  or  muscular 
asthenopia,  and  says  that  muscular  asthenopia  is  due  to  "insufficient 
contractile  force  of  the  interni  recti."  His  only  test,  like  that  of 
Wells,  was  the  dot  and  line  of  von  Graefe  and  made  at  a  distance  of 
15  centimeters  from  the  eyes. 

Landolt3  defined  muscular  asthenopia  as  "insufficiency  of  the 
internal  recti  muscles."  In  later  writings  he  lays  much  stress  upon 
"insufficiency  of  convergence,"4  but  he  had  not  when  my  classification 
of  these  anomalies  was  published,  modified  his  definition.  Stellwag5 
said :  "The  immediate  cause  of  asthenopia  is  always  the  overburden- 
ing of  the  muscle  of  accommodation,  or  of  the  internal  recti,  as  the 
case  may  be."  In  a  single  sentence  in  one  edition  there  appears  a 
recognition  of  "insufficiency  of  the  externi"  as  a  possible  cause  of 
asthenopia. 

Schweigger6  in  his  work  on  "Squint"  devoted  a  chapter  to  "Mus- 
cular Asthenopia,"  which  he  attributed  solely  to  insufficiency  of  the 
interni. 

These  representative  authors  fairly  indicate  the  views  of  all,  and 
their  views  show  the  importance  attached  to  the  conditions  since 
known  as  heterophoria  and  that  what  was  known  as  insufficiency  of 
the  externi  was  in  fact  a  difficulty  in  holding  the  eyes  converged  for 
a  very  near  point. 

The  system  which  is  included  in  this  work  had  gradually  devel- 
oped under  my  observations  until  in  1886  when  the  terminology  of 
heterophoria  was  published,7  after  which  a  series  of  papers8  on  the 
"Anomalies  of  the  Ocular  Muscles"  developed  the  system  to  an  ad- 
vanced point. 


1  "Diseases  of  the  Eyes." 

2  "Maladies  des  Yeux,"  pp.  739  and  789. 

s  "Manual  of  Examination  of  Eyes,"  translated  by  Burnett. 
*  "L' Amplitude   de    Convergence,"    1885 ;    "Insufficient    Power   of   Conver- 
gence," 1886;    "Refraction  and  Accommodation  of  the  Eye,"  1886,  etc. 
5  "Diseases  of  the  Eyes." 
•London  translation,  1887. 

7  Archives  d'Ophthalmologie,  November,  1886;   New  York  Medical  Jour- 
nal, December,  1886. 

8  In  Archives  of  Ophthalmology,  New  York,  commencing  1887. 


HISTORICAL  NOTES.  19 

The  condition  now  known  as  hyperphoria  had  never  been  referred 
to  in  the  literature  of  the  profession  under  any  name  previous  to  my 
own  description  of  it.1  Vertical  strabismus  was  well  known.  Hyper- 
phoria or  any  condition  to  which  the  term  is  now  applied  was  abso- 
lutely unknown. 

The  condition  of  esophoria  was  also  not  recognized. 

This  statement  is  made  with  due  consideration  of  all  the  facts. 
Von  Graefe,  it  is  true,  mentioned  in  a  single  paragraph  "insufficiency 
of  the  externi,"  but  the  quotations  which  have  been  made  above  show 
in  the  most  positive  manner  that  only  a  moderate  squint  was  indi- 
cated by  the  term.  When  he  wrote  that  his  patient  would,  after  the 
tenotomies  of  the  externi,  "be  just  able  to  fix  for  the  distance  though 
with  the  greatest  possible  strain  of  his  abducting  power,  to  which, 
as  ice  have  already  found,  there  is  no  objection''  he  placed  his  views 
definitely  on  record. 

A  few  other  writers  alluded  to  the  condition  of  "insufficiency  of 
the  externi''  generally  as  a  condition  which  might  be  found  by  placing 
a  red  glass  before  one  eye.  when  homonymous  diplopia  would  be  mani- 
fest. One  of  these  writers,  more  specific  than  others,  states  that  in 
his  case  there  was  30°  of  homonymous  diplopia.  Another  reports  an 
operation  for  insufficiency  of  the  externi  on  a  myopic  girl  who  had 
homonymous  diplopia  the  degree  of  which  is  not  stated. 

Of  course  such  cases  would  not  for  a  moment  now  be  regarded  as 
anything  but  somewhat  inconspicuous  cases  of  converging  squint. 

Since  hyperphoria  was  not  recognized  there  could  have  been  no 
recognition  of  the  conditions  now  recognized  as  hyperesophoria,  etc. 

We  come  now  to  the  only  condition  previously  recognized  which 
can  be  regarded  as  in  any  way  included  within  my  classification  of 
188G,  and  we  find  that  while  "exophoria"  may  be  included  in  the  very 
indefinite  condition  then  known  as  "insufficiency  of  the  interni/'  it 
does  not  by  any  means  signify  the  same  thing.  The  condition  known 
to  von  Graefe,  and  which  may  be  found  by  the  dot  and  line  test,  in- 
cludes all  the  way  from  a  mild  diverging  strabismus  to  decided  eso- 
phoria. It  is  not  at  all  uncommon  for  persons  with  high  degrees  of 
esophoria  to  show  the  so-called  "insufficiency  of  the  interni"  by  the 
dot  and  line  test. 

Tims  it  is  seen  that  of  the  conditions  in  my  classification  only 
one  can  by  any  stretch  of  courtesy  be  considered  as  a  condition  pre- 


1  Essay    on   "Functional   Nervous   Diseases."      Submitted    to    the    Royal 
Academy  of  Medicine  of  Belguim,  December,  1883. 


20  INTRODUCTION. 

yiously  recognized,  and  that  one  is  so  restricted  and  defined  in  the 
classification  that  it  is  no  longer  the  old  condition.  It  follows  that 
in  the  classification  of  heterophoria  the  new  terminology  was  not 
designed  to  apply  to  familiar  conditions,  but  was  the  expression  of 
new  facts  by  new  terms. 

Much  more  than  twenty-five  years  ago  I  reported  operations  for 
the  correction  of  definite  degrees  of  "insufficiency  of  the  externi," 
much  less  than  strabismus.  In  1881,  at  the  International  Medical 
Congress  held  in  London,  I  reported  other  such  cases  of  operative 
treatment,  and  in  the  essay  which  received  the  award  at  the  compe- 
tition on  the  subject  of  "Functional  Nervous  Diseases"  offered  by  the 
Royal  Academy  of  Medicine  of  Belgium,  1883,  315  cases  of  operative 
treatment  were  reported. 

These  were  the  first  single  cases  and  this  was  the  first  series  of 
cases  of  operations  for  definite  non-strabismic  "insufficiencies  of  the 
extern!."  In  the  prize  essay  just  mentioned  was  also  the  earliest 
recognition  of  the  condition  now  known  as  hyperphoria,  as  distin- 
guished from  vertical  strabismus. 

The  proposition  which  constituted  the  central  thought  of  that 
essay  was,  that  difficulties  of  the  adjustments  of  the  eyes  are  a  source 
of  nervous  trouble,  and,  more  frequently  than  other  conditions,  con- 
stitute a  neuropathic  tendency. 

In  the  development  of  this  proposition,  which  has  continued  dur- 
ing all  these  years,  a  refinement  of  methods  of  examination,  of  ter- 
minology, and  of  treatment  have  led  to  results  which,  in  the  early 
stages  of  the  investigations,  were  little  anticipated. 

It  will  not  be  out  place  here  to  present  in  brief  a  summary  of 
the  difference  between  the  views  which  I  have  presented  in  progressive 
stages  since  1880  and  those  which  were  previously  held.  And,  since 
no  one  had,  up  to  that  time,  materially  added  to  or  modified  the  doc- 
trine of  von  Graefe  his  views  are  accepted  as  those  held  by  ophthal- 
mologists. 

The  radical  difference,  then,  between  the  views  taught  by  von 
Graefe  and  the  system  which  has  been  developed  in  my  contributions 
lies  primarily  in  the  fact  that  that  great  authority  sought  to  adjust 
the  eyes  for  the  very  near  point  at  any  sacrifice  of  the  relations  of  the 
visual  lines  at  greater  distances  short  of  inducing  the  annoyance  of 
diplopia.  His  examinations  at  a  distance  were  not  in  the  interest  of 
actual  equilibrium  of  the  ocular  muscles,  but  in  respect  mainly  to  the 


HISTORICAL  NOTES.  21 

question  of  how  much  could  be  sacrificed  to  establish  convergence  at 
the  reading  point. 

In  the  system,  the  elements  of  which  I  have  from  time  to  time 
presented,  the  ideal  sought  is  the  perfect  equilibrium  of  all  the  mus- 
cular tensions,  in  all  respects,  in  vertical  as  well  as  in  lateral  direc- 
tions, so  that  without  violence  to  any  of  the  laws  of  movement  of  the 
eyes  they  may  adjust  in  all  parts  of  the  field  of  regard  without  incon- 
venience and  without  irregular  torsions. 

Yon  Graefe,  with  others,  spoke  of  "equilibrium"  of  the  ocular 
muscles,  but  their  tests  were  for  something  else.  They  regarded  the 
ability  to  direct  the  axes  of  the  two  eyes  to  the  same  point  at  the  usual 
distance  of  reading  for  the  individual  as  a  practical  standard  of 
equilibrium,  a  standard  to  be  gained  at  all  hazards. 

Passing  to  the  further  stages  in  the  evolution  of  the  doctrines  of 
anomalies  of  the  ocular  muscles  I  trust  that  I  may  not  incur  the 
charge  of  egotism  if  I  mention  these  stages  of  progress  as  I  have 
myself  suggested  them. 

With  the  refinements  of  diagnosis  came  refinements  of  therapeu- 
tics and  operative  procedures.  The  method  of  Dieffenbach  and  of 
von  Graefe,  of  severing  a  tendon  from  its  insertion  into  the  sclera 
was  seen  to  be  a  mutilation.  More  delicate,  more  exact,  and  far  more 
effective  operative  methods  were  adopted,  and  to  this  end  more  delicate 
and  far  better  constructed  instruments  were  required. 

In  examinations  systematic  accuracy  was  sought  in  the  use  of 
the  phorometer. 

Xotwithstanding  all  these  refinements  it  was  evident  that  there 
were  anomalous  elements  in  many  of  the  cases  which  were  either  out- 
side those  which  had  already  been  classified  or  that  these  known  ele- 
ments were  not  completely  understood.  It  now  seems  curious  that 
with  this  knowledge  and  with  an  earnest  desire  to  solve  the  problem 
of  the  exceptions  to  the  ordinary  rules,  the  conditions  which  we  may 
now  easily  discover  by  the  tropometer  were  not  appreciated  until  the 
conditions  of  heterophoria  had  been  diligently  studied  during  more 
than  fifteen  years.  Before  the  tropometer  was  brought  into  use, 
however,  anomalies  of  the  upward  and  downward  directions  of  the 
optic  axes  had  been  recognized  by  me  and  tested  rudely,  and  had  even 
been  found  to  be  important  elements  of  strabismus.1  When  at  length 
the  instrument  came  into  existence,  it  shed  such  a  flood  of  light  upon 


1  See  Transactions  of  International  Ophthalmological  Congress,  1894,  and 
Annales  d'Oculistique,  April  and  June,  1895. 


22  INTRODUCTION. 

many  obscure  questions  that  for  a  time  it  seemed  as  though  the  key 
had  been  found  which  would  unlock  the  secrets  that  had  been  so  long 
concealed.  The  normal  and  the  anomalous  positions  of  the  plane  of 
vision  were  now  first  defined  and  the  importance  of  the  conditions 
anophoria  and  katophoria  were  shown.1 

A  year  of  work,  while  progressively  showing  new  revelations  and 
fresh  explanations  of  many  problems,  showed  that  beyond  the  phe- 
nomena revealed  by  the  phorometer,  and  beyond  those  shown  by 
the  tropometer,  there  must  still  be  a  field  of  research  not  yet  opened. 

Helmholtz  and  other  philosophers  had  investigated,  from  a  phys- 
iological point  of  view,  the  directions  of  the  apparent  meridians  of 
the  retina.  Notwithstanding  the  crudity  of  his  methods  and  the 
paucity  of  observations,  Helmholtz  had  based  his  grand  theory  of 
the  horopter  on  the  results  of  his  researches  respecting  his  own  eyes.. 
The  fact  that  the  adjustments  of  his  eyes  might  not- represent  the 
best  normal  for  ocular  adjustments  did  not  occur  to  him  and  was  not 
taken  into  account.  When  in  listening  to  the  conversation  of  a  bore 
he  incontinently  multiplied  his  misfortune  by  seeing  two  bores  be- 
fore, him,  or  when,  after  a  frugal  dinner  at  which  wines  had  cut  no 
especial  figure,  all  his  friends  about  the  table  assumed  the  aspect  of 
Siamese  twins,  he  attributed  the  phenomenon  to  no  defect  of  his  own 
eyes,  but  appeared  to  think  that  it  was  the  way  that  eyes  were  made. 
It  was  to  him  simply  a  phenomenon  in  physiological  optics.  Hence, 
failing  to  realize  his  own  visual  peculiarities,  he  drew  conclusions 
from  his  observations  which  could  not  be  verified  by  others,  and  thus 
one  of  the  masterpieces  of  his  great  genius  was  rejected  as  of  no 
physiological  importance,  as,  in  a  technical  sense,  it  really  was.  I 
need  not  in  this  place  refer  to  the  investigations  of  Bonders,  Hering, 
Volkmann,  LeCompt,  and  others  in  this  field,  all  of  whom  were  in- 
fluenced by  the  same  misapprehension.2 

It  was  in  considering  how  it  happened  that  this  grand  labor  had 
failed  that  the  idea  of  a  practical  and  exact  method  for  making  the 
essential  examinations  was  suggested.  The  result  was  the  clinoscope. 
It  was  devised  as  an  instrument  for  the  study  of  a  technical  phys- 


1  Annales  d'Oculistique,  April  and  June,  1895. 

2 1  have  included  among  the  pioneer  observations  only  those  which,  had 
the  phenomena  been  studied  more  accurately,  might  have  led  to  the  discovery 
of  true  declinations.  Crude  theories  of  disabilities  of  the  oblique  muscles,  based 
on  experiments  in  which  the  elementary  principles  of  investigation  were  dis- 
regarded, since  they  could  neither  have  suggested  nor  aided  in  revealing  the 
real  nature  of  these  anomalies,  require  no  mention  here. 


HISTORICAL  NOTES.  23 

iological  phenomenon.  It  soon  became  the  means  for  making  a  class 
of  examinations  of  the  most  practical  character  which  go  farther  to 
explain  the  phenomena,  not  only  of  heterophoria,  but  of  strabismus, 
than  all  the  instruments  and  means  of  examinations  that  had  gone 
before. 

This  is  not  the  place  for  detail.  It  is  only  possible  to  touch 
upon  generalities,  and  those  only  in  most  comprehensive  terms. 

Yet,  to  illustrate  what  is  meant  by  the  remark  just  made,  I  will 
venture  a  single  detail  as  an  example. 

For  many  years  previous  to  the  introduction  of  the  clinoscope 
it  had  appeared  to  me  that  the  condition  which  we  knew  as  exophoria 
was  not  an  ultimate  and  independent  condition.  This  view  had  more 
than  once  been  expressed  in  my  writings  and  I  had  hoped  that  the 
reason  for  its  manifestations  might  be  discovered  in  some  more  pri- 
mary state.  If  now  we  search  for  that  primary  state  by  the  aid  of 
the  clinoscope,  we  will  be  likely  to  find  that  the  vertical  meridian  of 
each  eye  leans  outward,1  that  is,  there  is  positive  declination  in  each 
eye.  Xow,  if  we  consider  for  a  moment  the  legitimate  result  of  such 
a  position  of  the  vertical  meridians,  an  explanation  of  the  exophoria 
will  be  at  hand. 

There  is  no  stronger  visual  impulse  than  that  of  maintaining  the 
uprightness  of  the  images  perceived  by  the  eye.  A  leaning  of  the 
image  of  one  eye  or  those  of  both  eyes  means  to  the  possessor  of  that 
or  "of  those  eyes  that  the  earth  has  lost  its  equilibrium,  that  walking  is 
difficult  or  unsafe  and  that  surrounding  buildings  threaten  to  fall. 
Compare,  in  this  respect,  the  state  of  the  patient  with  paralysis  of  an 
oblique  muscle.  To  avoid  this  most  unpleasant  impression  the  mus- 
cles which  are  most  influential  in  rotating  the  eye  upon  its  axis  are 
brought  into  active  contraction.  With  the  contraction  of  these  mus- 
cles something  beyond  the  simple  rolling  of  the  eye  upon  the  optic 
axis  occurs,  namely,  a  turning  of  the  eyeball  down  and  out.  In  other 
words,  if,  with  positive  declination  of  the  vertical  meridians  of  the 
two  eyes  the  horizontal  and  vertical  meridians  are  forced  into  the 
appropriate  positions  for  receiving  the  horizontal  and  vertical  lines 
of  images,  there  will  result  a  tendency  of  the  eyes  to  swing  outward  in 
proportion  to  the  amount  and  symmetry  of  the  declinations.  Prac- 
tical observations  in  large  numbers  have  shown  that  this  is  the 


1  Among  the  cases  usually  met  with  in  private  practice  the  opposite 
condition,  double  negative  declination,  is  much  more  rare,  for  ethnological 
reasons. 


24  INTRODUCTION. 

general  law  of  exophoria.  Others  of  the  deviating  tendencies  and 
of  the  actual  deviations  of  the  eyes  can  he  explained  on  similar 
principles,  and  I  am  sure  that  I  shall  make  no  mistake  in  saying, 
that  when  the  excesses  or  deficiencies  of  vertical  rotation  of  the  eyes 
are  considered  in  connection  with  the  normal  declinations  of  the 
retinal  meridians,  it  will  be  no  longer  necessary  to  perform  the  well- 
known  and  standard  operations  for  converging  or  diverging  squint. 

This  statement,  while  strictly  conforming  to  the  theory  of  the 
actions  of  the  muscles,  is  not  an  hypothesis  built  solely  on  that  theory, 
but  is  the  actual  growth  from  the  experience  of  every-day  work. 

Thus,  by  the  knowledge  and  the  proper  interpretation  of  the  ver- 
tical rotations  of  the  eyes,  as  shown  by  the  tropometer  and  by  the 
corresponding  knowledge  and  interpretation  of  the  relations  of  the 
vertical  meridians  to  the  cranium  as  revealed  by  the  clinoscope,  we 
are  able  to  place  the  various  phenomena  of  heterophoria  and  of 
heterotropia  in  their  exact  physiological  relations  with  each  other, 
and  to  discover  that  various  forms  of  anomalies  are  not  isolated  facts, 
but  a  class  of  phenomena  so  well  arranged  and  so  interdependent  that 
a  knowledge  of  them  fairly  constitutes  a  science. 

Let  it  not  be  supposed  that  the  existence  of  such  a  science  has 
its  bearing  simply  in  the  realm  of  the  immediate  affections  of  the 
eyes.  The  influence  of  this  science  extends  as  far  as  the  jurisdiction 
of  the  nervous  system. 

The  conservatism  which  comes  with  a  good  many  years  of  hard 
experience,  not  by  any  means  free  from  sore  disappointments,  does 
not  lead  to  exuberant  declarations  of  things  hoped  for  but  which  are 
in  reality  only  the  active  workings  of  a  lively  imagination.  I  speak 
the  words  of  truth  and  sobriety  when  I  say  that  oculists  will  in  the 
near  future  hold  closer  relation  to  the  general  physical  well-being  of 
their  patients  and  of  the  community  than  any  other  class  of  medical 
practitioners,  except  those  who,  as  general  practitioners,  are  called 
first  in  every  form  of  ailment. 

Glance  for  a  moment  in  a  single  direction. 

There  is  a  class  of  boys  and  girls  who,  whether  standing,  walking 
or  sitting,  throw  the  forehead  far  in  advance  and  the  chin  into  the 
breast.  They  are  everywhere,  especially  in  our  Northern  States. 
Intellectually,  they  are  the  brightest  of  their  class.  Their  shoulders 
bend  with  their  heads  and  they  are  charged  by  their  friends  in 
constantly  reiterated  exhortations  to  stand  up  straight  and  hold  the 
shoulders  erect.  No  amount  of  admonition  does  any  good,  they  see 


HISTORICAL  NOTES.  25 

easier  when  the  head  is  advanced.  If  these  young  people  are 
examined  it  will  be  found  by  the  tropometer  that  they  all  have  the 
eyes  adjusted  for  a  plane  much  higher  than  the  horizon,  or  that  in 
certain  cases  there  is  notable  anomalous  declination  of  a  character  to 
induce  a  similar  bodily  pose.  It  is  often  the  penalty  for  a  head  in 
which  the  process  of  evolution  has  carried  the  axes  of  the  orbits  too 
far  from  the  original  low  plane  of  the  distant  ancestors  of  these 
young  persons. 

Can  the  pose  of  these  young  people  be  changed?  By  a  slight 
relaxation  of  the  superior  recti  muscles,  or  by  a  correction  of  the 
declination,  the  chin  will  lift  as  if  by  magic.  But  what  harm  can 
come  from  the  projecting  forehead  and  receding  chin?  Is  it  not  easy 
to  see  that  the  position  of  the  head  causes  the  upper  air  passages  to 
shut  like  a  valve?  The  hinge  is  at  the  larynx.  Xot  all  such  persons 
suffer  the  full  penalty  for  this  restriction  in  the  act  of  respiration,  but 
too  many  do. 

If  we  visit  one  of  the  modern  hospitals  for  consumptives  the 
most  striking  thing  to  a  close  observer  will  be  this  prevailing  pose  of 
the  head,  and  this  mechanical  obstruction  of  the  larynx. 

Could  those  heads  have  been  raised  and  could  those  shoulders 
have  been  made  erect  before  they  finally  caved  in?  In  a  short  time 
and  by  a  safe  and  painless  process.  Would  the  patient  have  had  con- 
sumption had  this  been  done  in  time  ?  I  can  only  say  that  by  the  cor- 
rection of  the  anophoria,  and  of  the  declination  which  sometimes  has 
a  like  effect  on  the  pose  of  the  head,  more  would  have  been  accom- 
plished than  by  any  change  of  climate  or  any  medical  regime  that 
could  have  been  prescribed. 

Perhaps  some  one  will  reply :  "Consumption  is  the  effect  of  the 
presence  of  bacilli  in  the  lungs." 

We  have  seen  a  field  wThere  a  farmer  has  just  burned  his  piles 
of  brush.  We  have  observed  the  blackened  soil  sprinkled  with  the 
white  ashes  where  the  brush  heaps  were  burned.  If  we  pass  the  same 
place  the  next  year  or  the  year  after  we  will  see  that  where  the  fires 
were  are  thick  masses  of  the  purple  flowering  fire-weed — epilobium — 
completely  covering  the  fired  spots.  It  grows  nowhere  else  in  the 
field.  But  the  epilobium  seeds  were  carried  by  the  wind  all  about. 
Why  do  they  spring  only  where  the  soil  has  been  burned?  The  soil 
of  these  spots  is  exactly  suited  to  the  growth  of  the  epilobium,  just 
as  the  mucous  membrane  in  the  quiet  eddies  of  a  half-filled  lung  is 
best  suited  to  the  propagation  of  the  consumption  bacillus. 


26  INTRODUCTION. 

It  is  very  certain  that  we  do  not  often  see  consumptives  who 
hold  the  chin  high  in  the  air.  In  other  words,  we  do  not  see  consump- 
tives whose  eyes  are  adjusted  below  the  plane  of  the  horizon.  The 
oculist  can  adjust  the  eyes  for  the  plane  of  the  horizon,  or  if  he 
desires,  which  I  hope  he  would  not,  for  a  plane  far  below  it. 

This  is  but  a  single  glance  in  a  single  direction,  and  one  may 
find  startling  truths  in  many  directions  if  one  will  look  with  the 
mental  vision  open  to  what  is  to  be  seen. 

If  it  is  thought  that  my  picture  is  a  fancy  sketch  it  will  require 
no  very  long  series  of  observations,  if  one  observes  well,  to  reach 
the  conclusion  that  I  have  drawn  but  a  rude  outline  of  a  realistic 
portrait. 

Looking,  then,  over  the  great  field  which  is  opened  by  the 
knowledge  of  the  relations  of  the  eyes  to  the  general  nervous  economy. 
we  see  that,  when  the  first  eye  flew  into  place  under  the  instruments 
of  Dieffenbach,  there  was  started  a  course  of  investigation  which,  with 
varying  fortunes  of  halting,  retreating  and  advancing,  has  led  to 
results  which  are  infinitely  more  far-reaching  than  appeared  to  his 
astonished  vision,  results  which  it  is  the  province  and  the  privilege 
of  the  skilled  surgeon  to  carry  to  higher  and  yet  higher  attainments. 

That  branch  of  medical  science  which  brings  its  votaries  in 
closest  relation  with  the  study  of  the  highest  of  physiological  actions, 
and  with  the  solution  of  most  interesting  questions  of  physiological 
psychology  and  of  physiological  optics;  with  the  study  of  the  express- 
ions of  the  face  and  with  the  types  of  the  cranium,  and  which,  there- 
fore, leads  to  interesting  and  practical  investigations  in  physiognomy 
and  craniology;  which  is  in  the  highest  sense  both  mathematical  and 
mechanical  and  which  demands. of  its  practitioners  the  highest  origin- 
ality of  method  and  the  greatest  refinement  in  execution;  which 
requires  of  its  servants  ability  to  adjust  themselves  to  constantly 
recurring  new  situations  and  to  form  logical  conclusions  from  their 
personal  observations,  leading  them  out  of  the  beaten  path  into  new 
and  enticing  fields ;  that  branch,  beyond  all  question,  is  the  one  which 
deals  with  the  relations  of  the  eyes  to  each  other  and  of  those  relations 
to  the  system  at  large. 


Effigiem   Taylor   tibi  qui   demissus    ab   alto   est, 

Turba  alias  expers  luminis,  ecce  videt, 
Hie  Maculas  tollitt,  Cataractas  deprimit  omnes 

Amissum  Splendens  excitat  ille  Tubar. 
Miranda  praxi  Sublata  Ophthalmia  qusevis 

Artifici  dextrae  gutta  Serena  Cedit 
Ecce  Virum!     Cujus  cignatur  tempora  lauro 

Dignum,  cui  laudes  saecula  tonga  canent. 


HISTORICAL  NOTES.  27 

Since  writing  this  introduction  I  have  had  the  good  fortune  to 
come  into  possession  of  an  engraved  portrait  of  John  Taylor,  who, 
whatever  may  be  our  conclusion  regarding  any  claim  in  his  behalf  that 
he  first  operated  by  tenotomy  of  the  lateral  musc'es  for  the  cure  of 
strabismus  or  whatever  view  we  may  take  of  his  code  of  ethics,  is  and 
must  always  be  a  personality  of  much  interest  to  all  who  may  be 
occupied  with  the  history  of  ophthalmology,  and  especially  with  that 
of  strabismus. 

This  old  print,  engraved  about  1745,  throws  some  additional 
light  on  the  peculiarities  and  the  work  of  Taylor.  We  have  the 
titles  of  several  of  his  works  and  we  have  the  inscription  laudatory  of 
his  accomplishments  and  abilities,  all  of  which  was  doubtless  directed 
by  Taylor  himself. 

It  is  to  be  recalled  that  in  Taylor's  time  fulsome  praise  of  this 
sort  accompanies  the  portrait  of  many  a  man  less  prominent  than  he — 
that  it  was  not  at  all  unusual  for  men  of  some  distinction  to  anticipate 
the  posthumous  fame  of  a  high-sounding  epitaph  by  inscribing  below 
their  "effig'es"  pretentious  and  magniloquent  panegyrics  of  them- 
selves. 

In  the  much-reduced  copy,  which  I  believe  will  be  of  interest  here, 
the  titles  of  the  works  have  been  rendered  so  inconspicuous  that  I 
transcribe  some  of  them  here. 

They  are,  in  part : — 

Taylor.     Mechanism  of  the  eye.     1727. 
On  the  muscles  of  the  eye.     1740. 
Mech.    del'Oeil.     1739. 
On  the  Mo —  Beauty  of  the  eye.     1744. 
Traite  de  Strabisme.    1733. 
On  the  Chrystallin —    1735. 
Mechan.    du  Globe  de  1'Oeil.     1737. 
Syllabus  Cursus  Anat:     1742. 

On  the  manuscript  at  the  left  is  inscribed,  "Coll:  of  the  Opin- 
ion of  the  Universities  on  his  Operations,  etc." 

"Sents.  of  the  University  of  Basle  in  Swizd.  Oct.  26,  1734,  when  admitted 
Doctr.  of  Physk." 

" of  Leige  Ap.  20,  1735." 

" of  Cologn  May  2.  1735,  both  in  Germany." 

".  . ! of  Caimbra,  Sept.  9th,  1738,  in  Portugual." 

If  Taylor  received  degrees  from  all  these  institutions  it  would 
seem  that  some  more  definite  knowledge  of  his  position  as  a  man  of 
learning  than  we  now  possess  might  be  obtained. 


PAET  I. 


ANATOMY  OF  THE  MOTOR  MUSCLES  OF  THE  EYES 
AXD  OF  THE  PARTS  ACCESSORY  TO  THEM. 

SECTION  I. 

MOVEMENTS  AND  POSITION  OF  THE  EYES. 

THROUGH  the  influence  of  the  various  muscles  attached  to  the 
globe  of  the  eye,  that  organ  executes  numerous  movements,  not  only 
upon  the  vertical  and  horizontal  axes  and  the  axes  approximating  to 
these,  but  also  upon  the  antero-posterior  axis.  Thus  the  eyes  move  in 
all  directions,  but  within  certain  limits.  In  different  species  of  verte- 
brate animals  we  observe  marked  differences  in  the  extent  of  these 
movements,  varying  from  those  scarcely  perceptible  to  those  greatly 
extended.  In  general  this  motile  ability  increases  as  the  species  to 
which  the  animal  belongs  rises  in  the  scale  of  organism.  More 
particularly  the  movements  of  the  eyes  are  greatest  in  those  species 
in  which  the  eyes  are  placed  most  anteriorly,  and  in  which  such  move- 
ments are  necessary  in  order  to  extend  the  field  of  regard. 

It  is  only  in  the  highest  order  of  vertebrates  that  the  rotary 
movements  of  the  eyes  reach  their  greatest  development. 

The  comparative  length  and  the  specialization  of  action  of  the 
muscles  controlling  these  movements  depend  largely  upon  the  posi- 
tion of  the  orbits  and  of  the  eyes  relatively  to  the  cranium. 

POSITION  or  THE  EYES  IN  ANIMALS. 

In  vertebrate  animals  the  eyes  are  situated,  in  general,  more  or 
less  laterally  and  upon  the  anterior  portion  of  the  cranium.  In  the 
lowest  orders  they  are  placed  quite  at  the  side,  in  the  highest  more 
anteriority.  As  the  animal  rises  in  the  scale  of  existence,  and  a?  it 
has  greater  occasion  to  direct  the  eyes  toward  the  front,  in  fact,  as 
the  animal  becomes  more  observant  of  special  objects,  the  axes 
approach  toward  parallelism.  In  proportion  to  this  parallelism  is  any 
considerable  range  of  binocular  vision  possible.  This  form  of  vision 

(28) 


COMPARATIVE  ANATOMY.  29 

is  found  principally  in  the  highest  animals  and,  except  within  narrow 
limits,  is  confined  to  that  class. 

Commencing  with  fishes,  in  which  class  the  axes  of  the  two  eyes 
are  almost  in  a  continuous  straight  line,  and  passing  to  reptiles,  in 
which  the  axes  form  an  obtuse  angle,  then  to  birds,  where  the  angle 
is  less  obtuse,  and  finally  to  the  class  of  mammals  in  which  the  axes 
approach  more  nearly  to  parallelism — as  a  rule,  with  an  angle  pro- 
gressively less  obtuse  as  the  animal  rises  in  the  scale  of  classification — 
there  is  found  with  these  modifications  in  the  directions  of  the  axes 
a  larger  motility  as  the  angle  becomes  less. 

From  a  cursory  glance  at  the  gradual  change  in  the  direction  of 
the  optical  axes,  it  would  be  easy  to  suppose  that  the  nearest  approach 
to  parallel  axes  would  be  found  in  man.  So  far  as  the  axes  of  the 
orbits  are  concerned  there  are  exceptions  to  this  rule  which  might  be 
based  upon  the  gradual  evolution  of  animal  types,  for  in  certain 
monkeys  and  apes  the  orbits  form  a  more  acute  angle  than  is  found 
in  man.  In  fact,  however,  while  the  divergence  of  the  orbital  axes  in 
those  species  in  which  they  approach  most  nearly  to  parallelism  is  less 
than  in  man,  the  axes  of  the  eyes  themselves  are,  in  these  lower 
animals,  more  divergent. 

SECTION  II. 

COMPARATIVE  ANATOMY  OF  THE  EYE  MUSCLES. 
PECULIARITIES  OF  THE  EYE  MUSCLES  IN  FISHES. 

There  are  six  muscles : — 

Four  recti,  analogous  to  those  in  man. 

Two  oblique,  also  analogous  to  those  in  man. 

The  origins  of  the  four  recti  differ  from  the  common  point  of 
origin  in  man,  in  that  while  in  man  all  the  recti  have  their  origin  in 
a  circle  around  the  optic  nerve,  in  fishes  the  points  of  origin  are 
behind  this  nerve.  The  extent  to  which  the  origins  are  posterior  to 
the  nerve  varies,  depending  upon  the  depth  of  the  sphenoidal  canal. 
In  the  species  in  which  this  canal  is  profound,  the  posterior  insertions 
are  found  within  it.  In  those  less  deep,  the  insertions  are  in  front 
of  the  canal.  In  the  first  group,  all  the  muscles  are  placed  very 
obliquely  to  the  axis  of  the  globe.  In  the  second  group,  the  four  recti 
muscles  are  nearly  parallel  with  the  axis. 

In  no  vertebrate  animals  are  the  superior  and  inferior  muscles 
parallel  with  the  axis,  they  are  always  obliquely  placed. 


30  ANATOMY. 

In  fishes  the  oblique  muscles  are  less  variable  than  the  recti. 
There  is  also  very  little  difference  of  length  and  size,  such  as  is  found 
among  mammals,  between  the  superior  and  inferior  oblique. 

There  is  no  pulley,  but  the  two  oblique  muscles  are  inserted  close 
together  at  the  antero-internal  angle  of  the  orbit,  and  are  diverted 
from  this  point  of  insertion  backward  and  outward  to  the  upper  and 
lower  faces  of  the  eyeball  and  to  the  portion  anterior  to  the  equator. 
Instead  of  exerting  a  force  toward  the  front  or  outward,  as  in  man, 
these  muscles  have  a  backward  energy.  They  are  inserted  in  advance 
of  the  insertions  of  the  recti ;  not  behind,  as  in  the  higher  vertebrates. 

In  certain  species  of  fishes,  strong  fasciculi  of  muscular  fibres 


Fig.  1. — Eye  Muscles  of  Cod  (Morrhua  Americana).     (Drawing  by  the 

Author.) 

constituting  accessory  muscles  divide  from  the  main  course  of  the 
recti  muscles  and,  instead  of  being  inserted  into  the  sclera,  unite  with 
the  capsule,  giving  an  appearance  of  a  double  set  of  recti  muscles, 
Fig.  1  shows  the  muscles  of  the  eye  in  the  cod.  The  course  of  the 
four  recti  is  more  nearly  analogous  to  that  in  man  than  that  of 
some  fishes,  and  they  pass  more  directly  backward.  The  origin  of  the 
muscles  is  not  shown,  but  the  posterior  extremities,  instead  of  taking 
their  origin  from  a  circle  around  the  nerve,  start  backward  further, 
finding  their  origin  in  the  sphenoidal  canal. 

PECULIARITIES  IN  AMPHIBIOUS  KEPTILES. 

Batrachians:  In  addition  to  the  four  recti  and  two  obliques, 
there  is  the  choanoideus,  which  has  the  effect  of  retracting  the  eye — 
a  muscle  having  a  greater  volume  than  the  recti  and  obliques  together. 


EYE  MUSCLES  OF  FISHES  AND  BIRDS. 


31 


This  funnel-shaped  muscle  first  appears  in  batrachians  and 
is  found  in  many  of  the  mammifers.  It  forms  a  ring  within  the 
circuit  of  the  recti  muscles,  being  inserted  into  the  sclerotic  at  its 
posterior  face,  and  having  its  origin  at  the  entrance  of  the  optic 
nerve  into  the  orbit,  is  divided  into  three  portions,  not  always,  how- 
ever, very  clearly  separated. 

The  posterior  superior  rectus  in  frogs  offers  the  first  suggestion 
of  the  peculiarity  of  arrangement  of  the  superior  oblique  in  man; 
starting  from  the  sphenoid  its  muscular  fasciculus  passes  outward 
and  upward,  is  directed  forward  and  upward  until  it  encounters  a 


Fig.  2. — Head  of  a  Frog  (Rana  fontinalis),  Showing  the  Muscles  of  One 
of  the  Eyes.  The  two  oblique  muscles  are  seen  to  proceed  from  a  common 
point  backward  to  be  inserted,  one  on  the  outer,  the  other  on  the  inner, 
side  of  the  eyeball  and  above  the  insertions  of  the  recti.  The  posterior 
rectus  passes  forward  from  the  sphenoid  until  it  encounters  a  transverse 
band  of  fibers,  where  it  changes  its  course  upward  to  be  inserted  into  the 
posterior  portion  of  the  globe.  The  clioanoideiis  is  seen  behind  and  below 
the  insertions  of  the  recti,  forming  an  envelope  for  the  optic  nerve.  The 
colors  of  all  the  muscles  are  purposely  exaggerated.  In  fact  the  color  is  a 
faint  pink.  (Drawing  by  the  Author.) 

strong  transverse  band  of  fibers  which  acts  as  a  sort  of  pulley.  The 
muscle  then  becomes  strongly  reflected  in  its  course,  passing  almost 
directly  outward  and  upward  to  its  insertion  in  the  posterior  portion 
of  the  anterior  hemisphere  of  the  sclerotic. 

The  retractor  muscle   (choanoideus)    serves  in  these  animals  to 
draw  the  eye,  usually  projecting,  to  the  plane  of  the  surface  of  the 


32  ANATOMY. 

cranium,  thus  protecting  the  organ  from  injury  in  the  case  of  its 
leapings,  diving  into  the  mud,  and  such  contingencies. 

In  frogs  (Fig.  2),  as  in  fishes,  the  two  oblique  muscles  are  in- 
serted in  advance  of  the  superior  and  inferior  anterior  recti  muscles, 
but  in  serpents  the  insertion  of  the  superior  oblique  is  sometimes 
behind  the  superior  anterior  rectus.  Here  is  the  first  indication  of 
the  position  of  the  oblique  muscles  of  the  higher  vertebrates  behind 
the  recti  muscles. 

PECULIARITIES  IN  BIRDS. 

In  birds  there  are,  as  in  fishes  and  reptiles,  six  muscles,  whose 
office  is  to  rotate  the  globe  of  the  eye. 

In  fishes  and  in  certain  reptiles  the  recti  muscles  find  their 
origin  far  posterior  to  the  optic  nerve.  In  some  reptiles  the  muscles 
arise  more  nearly  in  relation  to  this  nerve.  In  birds  the  muscles  com- 
mence in  a  circle  around  the  optic  nerve.  Beyond  this  there  is  no 
marked  peculiarity  in  the  direction  and  disposition  of  the  muscles 
as  compared  with  those  of  reptiles.  But  it  is  to  be  observed  that  in 
birds,  as  in  frogs,  the  superior  oblique  is  inserted  somewhat  poste- 
riorily  to  the  superior  rectus.  Its  insertion  into  the  sclera  is  very 
extensive,  starting  as  far  forward  as  the  insertion  of  the  superior 
rectus  and  extending  over  this  muscle  and  backward  behind  the 
equator. 

The  muscles  are  named,  respectively,  the  anterior  rectus,  poste- 
rior rectus,  inferior  and  superior  rectus,  with  the  superior  and  inferior 
oblique  muscles.  The  anterior  corresponds  to  the  internal  rectus  in 
man,  the  posterior  to  the  external.  The  insertion  of  the  anterior 
rectus  is  considerably  nearer  to  the  superior  than  to  the  inferior 
oblique.  The  posterior  rectus  is  attached  to  the  posterior  portion  of 
the  eyeball  and  rounding  the  convexity,  passes  under  the  eye  to  the 
border  of  the  optic  foramen. 

The  shortness  of  the  muscles  and  the  fact  that  the  eye,  to  a  very 
great  extent,  fills  the  orbit,  serve  to  limit  the  motility  of  the  eyes 
materially,  so  that  the  ocular  movements  are  actually  very  slight. 

It  is  noticeable  that  birds  which  hunt  their  prey  from  great 
heights  have  very  large  eyes  and  very  slightly  developed  eye  muscles; 
while  waders  and  birds  which  seek  for  food  at  little  distance  have 
smaller  eyes  and  more  fully  developed  muscles. 

Fig.  3,  representing  the  head  of  the  winter  gull,  Larus  argen- 
tatus,  shows  a  dissection  of  the  eye  muscles.  It  is  seen  that  the  four 


EYE  MUSCLES  IN  BIRDS. 


33 


recti  pass  backward  to  the  foramen  for  the  optic  nerve  and  are 
inserted  about  the  entrance  of  this  nerve  to  the  orbit.  The  two 
oblique  muscles  pass  from  the  upper  and  lower  border  of  the  eyeball 
forward  to  be  inserted  into  the  anterior  part  of  the  orbit. 

PECULIARITIES  IN  MAMMALS. 

There  are  in  certain  mammals  seven  ocular  muscles:  four  recti, 
two  oblique,  and  the  choanoideus,  which,  as  we  have  already  seen, 
is  found  also  in  certain  reptiles.  This  seventh  muscle  is  present  in 


Fig.  3. — Head  of  Winter  Gull  (Larus  argentatus),  Showing  a  Dissection 
of  the  Eye  Muscles.     (Drawing  by  the  Author.) 

very  many  of  the  lower  species  of  mammalia;  but  although  found  in 
lemurs,  has  not  been  observed  in  monkeys,  except  in  rare  cases 
when  it  consists  of  a  small  fasciculus.  It  is  most  prominently 
developed  among  ruminants.  In  those  species  in  which  it  is  prin- 
cipally developed,  Motais1  found  its  origin  not  only  from  around 
the  optic  foramen,  but  still  more  from  the  sphenoidal  canal,  from 
which  a  very  large  portion  of  the  fibers  emerges  in  close  relation  with 
the  third  and  sixth  nerves.  It  surrounds  the  optic  nerve  in  its  out- 
ward course  as  an  enveloping  cone,  and  it  is  inserted  into  the  pos- 
terior portion  of  the  sclera  in  a  somewhat  irregular  ring  (Fig.  4). 
Its  office  appears  to  be  to  draw  the  eye  into  the  orbit  and  it  may  also 
act  as  the  organ  of  suspension  for  the  eye.  It  is  in  close  relation  with 


1  Motais,  "Anatomie  de  1'Appareil  de  1'Oeil  de  1'Homme  et  des  VertSbres, 
Paris,  1887. 


34  ANATOMY. 

the  so-called  third  eyelid  which  exists  in  reptiles,  birds  and  some 
mammals,  and  in  proportion  to  the  development  of  one  is  that  of  the 
other  (Motais).  In  man  and  most  monkeys  in  which  the  third  eye- 
lid is  absent  there  is  also  an  absence  of  the  choanoideus. 

The  origin,  course  and  insertion  of  the  recti  muscles  are  analo- 
gous to  those  in  the  human  subject.  From  each  of  the  four  recti  in 
certain  species  there  arise  from  the  surface  of  the  muscle  bands  of 
fibers  which,  in  some  instances,  become  veritable  accessory  tendons 
connecting  the  muscles  with  the  walls  of  the  orbits.  Sappey  describes 
such  bands  arising  from  internal  and  external  recti  of  man.  Motais 


Fig.  4. — The  External  Muscles  of  the  Eye  of  the  Domestic  Sheep.  The 
superior  oblique  is  seen  to  be  inserted  in  front  of  the  insertions  of  the  recti 
instead  of  behind  them,  as  in  the  case  of  man.  The  external  rectus  is 
turned  aside  to  show  the  conical-shaped  choanoideus,  which  is  inserted 
into  the  posterior  portion  of  the  globe  and  envelopes  the  optic  nerve. 
(Drawing  by  the  Author.) 

asserts  that  he  has  found  similar  bands  from  each  of  the  four  recti  in 
man. 

The  oblique  muscles  no  longer  conserve  their  uniformity  of 
origin,  as  in  the  lower  orders.  The  inferior  oblique  maintains  its 
origin  at  the  anterior  border  of  the  orbit,  but  in  all  mammals  the 
superior  oblique  takes  its  origin  with  the  recti  muscles  at  the  pos- 
terior portion  of  the  orbit,  and  in  all  cases  the  muscle  takes  its  course 
through  a  pulley  in  or  near  the  superior  border  of  the  orbit  and  is 
reflected  backward  to  the  insertion  into  the  sclera. 

Only  in  monkeys  and  in  man  is  the  insertion  of  the  superior 
oblique  on  the  posterior  hemisphere  of  the  globe.  In  these  the  pulley 
is  placed  further  in  advance  and  the  insertion  more  posteriorly  on  the 


EYE  MUSCLES  OF  MAMMALS.  35 

globe.  Hence,  while  in  many  species  the  action  of  the  superior 
oblique  is  almost  in  a  transverse  direction,  in  the  highest  orders  it  is 
more  obliquely  from  before  backward.  In  my  dissections  I  find,  what 
I  have  not  seen  elsewhere  noted,  that  the  recti  muscles  are  loosely 
attached  to  the  eyeball  of  the  domestic  sheep,  the  insertion  being  into 
an  extremely  delicate  capsule  which  surrounds  the  eyeball  as  far  as 
the  cornea,  rather  than  into  the  sclera.  These  muscles  do  not  appear 
to  have  any  rotating  power  worth  considering.  The  oblique  muscles 
are  more  intimately  connected  with  the  sclera,  but  the  cartilaginous 
pulley  for  the  superior  oblique  is  buried  in  the  soft  orbital  tissues 
and  is  not  directly  attached  to  the  bone  of  the  orbit,  nor  has  it,  ap- 
parently, any  point  of  resistance.  As  seen  in  the  accompanying 
sketch  the  funnel-shaped  choanoideus  is  the  principal  muscle  of  the 
eye  and  it  is  more  directly  inserted  into  the  sclera  than  any  of  the 
others.  There  seems  to  be  no  reason  to  regard  the  recti  or  the 
oblique  muscles  of  the  domestic  sheep  as  little  more  than  as  vestiges 
of  organs  which  in  some  ancestral  animals  served  a  useful  purpose. 


SECTION  III. 

THE  ORBITS. 

The  eyes  are  surrounded,  protected,  and  indirectly  supported  by 
walls  built  from  many  separate  bones  which  together  form  somewhat 
pyramidal  cavities,  the  orbits,  the  apices  of  which  are  behind,  while 
the  bases  or  orbital  overture  are  toward  the  general  plane  of  the  face. 
These  cavities  are  somewhat  quadrilateral,  especially  toward  the  base. 
The  outer  walls  of  the  two  orbits  approach  each  other  as  they  extend 
backward,  while  the  inner  walls  are  nearly  parallel.  The  upper  wall 
also  descends  toward  the  apex,  the  lower  being  more  nearly  horizontal. 
The  axes  of  these  two  cones  or  pyramids  would,  if  extended  backward, 
according  to  Sappey,1  cross  each  other  very  nearly  at  the  basilar  apo- 
physis  of  the  occipital  bone.  Other  anatomists  place  the  crossing  of 
these  lines  at  the  center  of  the  sella  turcica  (Cruveilhier).2 

These  different  results  follow  from  the  choice  of  different  guiding 
marks  at  the  extremity  of  the  orbital  cavity;  for  while  some  anatomists 
have  selected  the  optic  foramen  as  the  point  through  which  the  axis 
should  be  prolonged,  others  have  selected  the  broader  portion  of  the 


1  Traite  d'Anatomie  Descriptive,  1868. 

2  Traite  d'Anatomie  Descrip.  t  ii,  partie  2e. 


36 


ANATOMY. 


sphenoidal  fissure ;  others  still  have  chosen  the  broader  portion  of  the 
spheno-maxillary  fissure,  while  a  fourth  group  of  observers  have  taken 
the  narrow  portion  of  the  same  fissure.  Even 'when  the  same  points 
are  selected  as  points  of  direction  there  is  found  a  variation  in  the 
angles  formed  by  the  axes  of  the  two  orbits  in  different  individuals, 
depending  on  the  general  form  of  the  skull,  a  variation  which  will 
throw  the  crossing  more  or  less  backward.  The  subject  of  the  angle 
formed  by  the  axes  of  the  orbits  and  the  plane  in  which  they  lie,  with 


Fig.  5.— The  Orbits. 

the  measurements  of  the  walls  and  openings,  will  be  considered  as  we 
proceed. 

Several  bones  enter  into  the  construction  of  the  orbit.  Thus  the 
roof,  the  largest  of  the  four  walls  (paries  superior),  is  formed  anteri- 
orly by  the  orbital  plate  of  the  frontal  bone,  and  more  posteriorly  by 
the  lesser  wing  of  the  sphenoid.  Below,  the  orbital  process  of  the 
superior  maxilla,  the  orbital  process  of  the  malar  bone  and  the  orbital 
process  of  the  palate  bone  constitute  in  their  order  from  before  back- 
ward the  floor  of  the  orbit  (paries  inferior).  The  wall  of  the  nasal 
side  (paries  medialis) ,  the  least  in  extent  of  the  four,  is  formed  mainly 
by  the  os  planum  of  the  ethmoid  and  the  orbital  surface  of  the  lachry- 


THE  ORBITS.  37 

mal.  From  before  backward  the  four  bones  entering  into  the  compo- 
sition of  this  wall  are :  the  nasal  process  of  the  superior  maxillary,  the 
os  unguis,  the  os  planum  of  the  ethmoid,  and  a  small  part  of  the  body 
of  the  sphenoid.  The  nasal  process  of  the  superior  maxilla  constitutes 
a  portion  of  the  inner  anterior  wall  as  well  as  a  portion  of  the  anterior 
floor.  The  lesser  wing  of  the  sphenoid  with  its  optic  foramen  forms 
the  posterior  portion,  not  only  of  this,  but  of  the  other  walls. 

The  greater  wing  of  the  sphenoid  and  the  malar  bone,  with  the 
temporal  extension  of  the  orbital  portion  of  the  frontal  bone,  consti- 
tute the  elements  of  the  exterior  wall  (paries  lateralis). 

The  inner  wall  has  a  thickness  of  from  2  millimeters  to  4  milli- 
meters, which  greater  thickness  is  posteriorly.  The  inferior  wall  is 


Fig.  6. — The  External  Wall  of  the  Orbit.  1,  Section  of  temporal  bone. 
2,  Orbital  surface  of  temporal  bone.  3,  Orbital  surface  of  malar  bone. 
4,  Section  of  Malar  bone.  5,  Infra-orbital  groove.  6,  Orbital  surface  of 
Greater  Wing  of  Sphenoid.  7,  Sphenoidal  fissure.  8,  External  orbital  fora- 
men. (Drawing  by  the  Author.) 

from  0.5  millimeter  to  1  millimeter  in  thickness,  while  the  outer  wall 
is  from  1.5  millimeters  to  2  millimeters,  and  the  superior  wall  is, 
like  the  inner  wall,  extremely  thin. 

At  the  apex  of  the  orbit  is  the  optic  foramen  for  transmission  of 
the  nerve  of  the  same  name  and  of  the  ophthalmic  artery.  This  optic 
foramen  is  in  fact  the  space  between  the  two  roots  of  the  lesser  wing  of 
the  sphenoid  bone.  A  tubercle  within  this  bony  wing  serves  as  an 
attachment  for  the  common  tendon  with  which  several  of  the  eye 
muscles  are  connected. 

In  these  orbital  walls  are  found  many  openings  besides  the 
optic  foramen,  among  which  are  principally  the  sphenoidal  fissure, 
nearly  vertical  and  anterior  and  external  to  the  optic  foramen, 


38 


ANATOMY. 


for  the  transmission  of  the  third,  the  fourth,  the  ophthalmic  portion 
of  the  fifth  and  the  sixth  nerves,  and  the  ophthalmic  vein.  In  fresh 
dissections  the  foramen  is  closed  by  a  layer  of  the  lining  membrane  of 
the  orbit  which  closely  envelopes  the  transmitted  nerves  and  vessels. 
In  the  lower  and  external  walls  is  the  spheno-maxillary  fissure  for  the 
passage  of  the  tempero-maxillary  and  the  malar  artery.  Besides  these 
are  several  other  openings,  among  which  are  the  foramina?  or  grooves 
in  the  superior  arches  for  the  exit  of  the  supra-orbital  nerves  and 
vessels. 


Fig.  7. — The  Internal  Wall  of  the  Orbit.  1,  Supra-orbital  margin  of 
frontal  bone.  2,  Spine  of  trochlea.  3,  Fronto-maxillary  suture.  4,  Lach- 
rymal groove.  5,  Lachrymo-ethmoidal  suture.  6,  Lachrymo-maxillary 
suture.  7,  Infra-orbital  margin.  8,  Infra-orbital  foramen.  9,  Ethmoido- 
maxillary  suture.  10,  Infra-orbital  groove.  11,  Optic  foramen.  12,  Pos- 
terior ethmoidal  fissure.  13,  Anterior  ethmoidal  fissure.  (Drawing  by  the 
Author.) 

A  fossa  just  within  the  lower  part  of  the  nasal  margin  of  the 
orbit  forms  the  bed  for  lodgment  of  the  lachrymal  sac ;  while  another 
fossa  situated  just  behind  the  border  at  the  superior  external  part  of 
the  orbit  is  the  location  of  the  orbital  portion  of  the  lachrymal  gland 
(the  lachrymal  fossette).  Somewhat  outside  the  border  of  the  floor 
of  the  orbit  is  situated  the  infra-orbital  foramen,  which  is  the  termina- 
tion of  the  infra-orbital  canal.  The  infra-orbital  groove,  or  sulcus, 
occupying  a  longitudinal  space  in  the  posterior  floor,  constitutes  a 


MEASUREMENTS  OF  THE  ORBITS.  39 

part  of  this  canal.  Inside  the  border  of  the  superior  floor  is  situated  a 
small  spine,  the  foundation  of  the  trochlea. 

Anteriorly,  the  boundaries  of  the  orbital  opening  are  more  or  less 
definitely  divided  into  four  parts  by  as  many  angles.  These  angles, 
of  which  the  two  superior  and  the  two  inferior  are  called  the  external 
and  internal  superior  and  the  external  and  internal  inferior  angles 
respectively,  are  to  a  considerable  extent  variable.  The  variation  may 
extend  even  to  the  effacement  of  all  -except  the  inferior  angle,  which 
is  always  present  as  an  angle,  and  is  hence  known  as  the  angle  of  the 
eye. 

The  projection  of  the  border  of  the  orbit,  forming  a  distinct  mar- 
gin around  most  of  its  circumference,  results  in  a  diminution  of  its 
size  at  its  anterior  overture,  the  diameter  being  greatest  at  a  little 
more  than  two-thirds  the  distance  from  the  posterior  extremity. 

The  upper  or  supercilliary  border  of  these  orbital  arcades,  formed 
from  the  frontal  bone,  projects  beyond  the  lower  border,  permitting  a 
range  of  vision  downward  greater  than  would  exist  were  the  lower 
border  equally  as  prominent  as  the  upper.  So  also  the  lateral  border 
is  several  millimeters  behind  the  medial  border.  Indeed,  the  whole 
general  form  of  the  orbit  is  such  as  to  permit  a  wide  range  of  move- 
ments of  the  globe  of  the  eye  and  of  a  field  of  regard  extended  in 
many  directions.  The  internal  border,  which  furnishes  an  important 
point  for  orbital  and  interorbital  measurements,  is  formed  by  the 
internal  orbital  process  of  the  frontal  and  the  nasal  process  of  the 
superior  maxillary  bones.  At  the  union  of  these  two  and  of  the 
lachrymal  bone  is  the  point  known  as  the  dacryon,  the  starting  point 
of  various  measurements.  The  distance  between  the  dacryon  of  one 
orbit  and  that  of  the  other  is  known  as  the  interorbital  space.  The 
form  of  the  orbital  overture  varies  from  nearly  round  to  almost  rec- 
tangular. 

MEASUREMENTS  OF  THE  ORBITS. 

The  results  of  measurements  of  different  parts  of  the  orbit  must 
vary  according  to  the  age  and  sex  of  the  individual  and  according  to 
race. 

Measurements  conducted  by  different  authors  have  not  been  alto- 
gether uniform,  and  the  methods  adopted  by  different  craniologists 
have  not  been  equally  satisfactory. 

Anteriorily  the  points  selected  as  fixed  points  in  the  measurements 
are  the  four  ang^s  (only  one  of  which  is,  however,  constant)  and  the 


40  ANATOMY. 

diameters  between  the  orbital  borders  between  these  angles.  Naturally, 
as  the  angles  are  often  badly  denned,  these  second  measurements  are 
equally  uncertain. 

Topinard1  adopts  the  following  points :  The  horizontal  diameter 
is  measured  from  the  dacryon  to  the  point  horizontal  with  and  opposite 
to  the  dacryon.  The  vertical  diameter  starts  from  the  lower  border  at 
the  spot  where  the  naso-maxillary  suture  meets  the  infra-orbital  edge 
and  cutting  perpendicularly  the  horizontal  diameter. 

The  greatest  diameter  in  height  and  the  greatest  diameter  in  the 
horizontal  direction  do  not  coincide  with  these  lines,  as  will  be  seen 
from  the  diagram  at  Fig.  8,  copied  from  Toldt's  "Atlas  of  Anatomy." 
Virchow  measures  the  greatest  horizontal  diameter  parallel  to  the  plane 
of  the  horizon  and  the  greatest  vertical  diameter  at  right  angles  to 
the  first.  Broca's  measurements2  are  nearly  those  described  by 
Topinard,  but  are  more  oblique,  like  those  on  the  right  in  the  Toldt 
diagram. 

Stilling,3  of  Strasbourg,  bases  upon  the  orbital  index  a  theory  of 
compression  of  the  globe  by  the  superior  oblique.  He  believes,  with- 
out sufficient  evidence,  that  a  low  index  predisposes  to  myopia,  and  the 
opposite  state,  a  high  index,  predisposes  to  hyperopia. 

Weiss  also  thinks4  that  the  orbit  is  lowor  in  myopes  than  in  hyper- 
opes,  the  capacity  of  the  orbits  in  the  former  being  less  than  in  the 
latter.  Weiss,  however,  does  not  concur  in  all  the  conclusions  of 
Stilling. 

Broca  and  other  craniologists,  in  comparing  the  various  measure- 
ments of  breadth  and  height,  employ  the  term  "orbital  index/'  which 
is  the  relation  of  the  horizontal  diameter  of  the  base  overture  of  the 
orbit  to  its  vertical  diameter.  (Fig.  8.) 

For  adults  of  Anglo-Saxon  lineage  the  dimensions  of  the  orbits 
may  be  contingently  stated  as  follows : — 

From  the  optic  foramen 

To  the  internal  angle  of  the  base,  about  45  mm. 
To  the  external  angle  of  the  base,  about  50  mm. 
To  the  middle  of  the  superior  arch,  about  52  mm. 
To  the  middle  of  the  inferior  arch,  about  52  mm. 


1  Topinard ;    "Anthropology." 

2  Eroca :    "Instructions  C'raniologiques  et  Craniometriques,"  p.  72. 

8  "tiber   Entstehung   der  Myopie."      Transactions    Seventh    International 
Ophthalmological  Congress,  Heidelberg,  1886. 

4  Weiss :  International  Ophthalmological  Congress,  Heidelberg,  1889. 


MEASUREMENTS  OF  THE  ORBITS. 


41 


The  measurements  of  the  diameters  of  the  orbit  are  as  varied  as 
those  of  the  length. 

In  the  future  chapter  it  will  be  shown  that  the  orbital  index 
varies  with  the  type  of  the  skull;  that  the  excursions  of  the  eyes  in 
the  vertical  directions  vary  correspondingly  to  the  type  of  the  orbit, 
and  therefore  largely  corresponding  to  the  type  of  the  cranium.  The 
orbital  index  of  the  young  child  exceeds  that  of  the  adult.  The  orbit 
of  the  infant  is  oval,  the  larger  part  being  the  temporal. 


Fig.  8. — Vertical  and  Transverse  Diameters  of  the  Orbit,  e  f  and  g  li,  the 
greatest  vertical  and  transverse  diameters  of  the  orbit,  according  to  Broca ; 
a  I),  c  (I,  the  direct  vertical  and  horizontal  diameters  of  Virchow.  (From 
Toldt's  Anatomical  Atlas.) 

Emmert,  of  Basle,  has  given1  the  results  of  his  examinations  of  44 
skulls  of  native  Swiss,  of  9  Turkish  soldiers  who  had  died  in  Switzer- 
land, and  of  11  other  persons  foreign  to  Switzerland.  He  averages  the 
results  under  five  groups,  of  which : — 

First  group  consists  of  19  native  Swiss,  from  0  to  17  years  of  age. 

Second  group,  10  native  Swiss  women,  from  23  to  77  years  old. 

Third  group,  15  native  Swiss  men,  from  20  to  67  years  old. 

Fourth  group,  9  Turkish  adults. 

Fifth  group,  11  other  foreign  adults. 


"Auge  und  Schiidel."    Emil  Emmert,  Berlin,  1880. 


42 


ANATOMY. 


The  interorbital  distance  in  Ernmert's  groups  he  found  as  repre- 
sented below : — 


Um»O.BITAL    DIST, 

NCF  •         FlKST  GROUP 

•          (Children) 

fS^J> 

THIRD  GROUP 

(Swiss  .Men) 

Average   .    .    . 

80.8  millimeters 

96.0  millimeters 

97.0    millimeters 

Greatest   .    .    . 
Least     .... 

.      96.0           " 
.      59.0           " 

103.5           " 

91.0           '• 

106.5             " 
91.75 

The  following  table  gives  the  results  of  the  average  measurements 
of  the  breadth,  height,  and  orbital  index^  and  also  of  the  cephalic  index 
of  these  groups. 

The  "orbital  index"  is  found  by  dividing  the  height  by  the 
breadth  and  multiplying  the  result  by  100 ;  or  by  the  formula,  100  : 
height : :  breadth :  index. 


ORBIT 

• 

FIRST  GROUP 
Infants   and 
Adults 

SECOND  GROUP 
Female  Adults 
(Swiss) 

THIRD  GROUP 
Male  Adults 

(Swiss) 

FOURTH  GROUP 
Adults 
(Turkish) 

FIFTH  GROUP 
Other 
Adults 

Breadth    .    . 

34.3  mm. 

39.8  mm. 

41.6  mm. 

40.65  nnii. 

42.8  mm. 

Height      .    . 

29.2    " 

33.6     " 

34.0     " 

34.40     " 

84.9     " 

Orbital  Index 

85.     . 

84.5 

81.7 

84.6 

81.6 

Cephalic  \ 
Index    /   ' 

81.3 

83.00 

83.4 

75.8 

75.7 

I  have  made  a  careful  analysis  of  the  individual  cases  reported  by 
Emmert  in  order  to  ascertain  the  comparative  orbital  index  to  the  type 
of  skull — an  analysis  which  Emmert  did  not  attempt — and  have 
compared  the  results  with  my  own  examinations  made  for  the  purpose 
of  ascertaining  the  direction  of  the  axis  of  the  orbit  in  respect  to  the 
horizon. 

If  we  class  skulls  having  the  cephalic  index  less  than  77.77  as  long 
or  dolicho-cephalic  heads;1  those  having  the  cephalic  index  from  77.78 
to  83.34  as  medium  or  meso-cephalic  heads,  and  all  above  83.34  as 
broad  or  brachy-cephalic  heads,  the  result  of  this  analysis  gives  us,  for 
Emmert's  cases,  the  following  table : — 


1  The  measurements  adopted  by  Topinard,  "Anthropology,"  p.  238. 


MEASUREMENTS  OF  THE  ORBITS. 


43 


Analysis  Inj  the  Author  of  Emmerfs  Examination  of  Forty-four  Skulls. 


TYPE  OF   SKULL 

Long 
(dolieho-cephalic) 

Medium 
(raeso-cephalic) 

Broad 
(  brachy-cephal  ic) 

Cephalic  Index  ...        , 

77.77  and   below 

77  78  to  83  34 

Above   83.34 

Average  Orbital  Index 

82.9 

87.00 

83.5 

Comparing  these  results  with  an  analysis  of  the  comparative  ceph- 
alic and  orbital  indices  found  by  myself,  using  the  methods  of  Broca, 
in  my  investigation  of  the  Normal  Directions  of  the  Planes  of  Vision 
in  Relation  to  Certain  Cranial  Characteristics,1  and  using  only  the 
40  crania  examined  at  the  Army  Medical  Museum  at  Washington,  com- 
prising C  Bavarians,  3  Austrians,  1  Japanese,  17  unclassified  whites, 
principally  Americans,  and  13  negroes,  we  have  the  following  table : — 

Analysis  of  Stevens' s  Examination  of  Forty  Skulls. 


TYPE  OF  SKULL 

Long 
(  dolicho-cephal  ic  ) 

Medium 

(meso-cephalic) 

Broad 
(brachy-cephalic) 

Cephalic  Index  .... 

77.77  and  below 

77.78  to  83.34 

Above  83.34 

Average  Orbital  Index  .    . 

79.9 

88.00 

82.25 

It  will  be  seen  that  two  investigators,  by  independent  methods, 
and  with  different  ends  in  view,  have  arrived  at  results,  so  far  as  the 
relative  forms  of  the  orbits  to  the  type  of  skull  are  concerned,  which 
are  remarkably  similar ;  for  while  the  figures  in  these  two  tables  differ 
slightly,  they  are  practically  in  harmony  in  showing  that,  with  the 
long  skull  the  orbit  is  low,  with  the  broad  skull  it  is  still  low  but  rather 
higher  than  in  case  of  the  long  skull;  while  in  the  medium  skull  the 
orbit  exceeds  either  of  the  other  forms  in  height  by  a  very  important 
measurement. 

These  peculiarities  in  the  form  of  the  orbit  are  not  merely  inter- 
esting coincidents,  they  are  characters  which  have  most  important  bear- 
ings upon  the  motile  condition  of  the  eyes,  as  will  be  seen  as  we  ad- 
vance. 


1  Archives  of  Ophthalmology,  No.  3,  1897. 


44  ANATOMY. 

The  following  figures,  drawn  from  crania  in  the  Army  Medical 
Museum  at  Washington,  will  serve  to  illustrate  the  three  characteris- 
tic types  of  crania  and  the  associated  types  of  orbits. 


Fig  9.  Fig.  10.  Fig   11. 

Figs.  9,  10,  11. — Characteristic  Forms  of  Orbits.  Fig.  9  shows  the  long  and 
oblique  orbit  of  the  long  skull;  Fig.  10,  the  much  higher  and  less  oblique 
form  of  that  of  the  medium  or  tall  skull,  and  Fig.  11,  the  long  and  oblique 
orbit  of  the  broad  skull,  somewhat  similar  to  that  of  the  long  skull,  but 
not  extending  as  low  at  the  temporal  side  and  being  less  triangular. 
(Drawings  by  the  Author.) 

PLANE  OF  THE  OPTIC  AXES. 

The  plane  of  the  axes  of  the  orhits  in  respect  to  the  horizontal 
plane  is  of  much  more  than  merely  ethnic  interest.  We  shall  see  that 
this  plane  doubtless  plays  a  part  of  great  importance  in  the  normal 
plane  of  regard,  and  that  upon  it  depend  some  of  the  most  important 
functional  peculiarities  with  which  the  practical  oculist  has  to  contend. 

For  the  method  of  Broca1  for  ascertaining  this  axis  the  reader  is 
referred  to  Fig.  12,  page  45,  where  Broca's  instrument  for  ascertain- 
ing the  direction  of  the  orbital  axis  is  shown  in  connection  with  the 
author's  craniostat. 

Broca  assumes  that  the  optic  axis  passes  in  a  line  cutting  the 
center  of  the  vertical  diameter  of  the  orbit  and  the  center  of  the  optic 
foramen.  In  the  figure,  the  star-shaped  body  serves  to  separate  the 
branches  to  the  extent  that  the  extremity  of  each  branch  is  in  con- 
tact with  the  orbital  border.  The  central  branch  will  then  be  situ- 
ated exactly  midway  between  the  two  outer  branches,  and  therefore 
in  the  outer  extremity  of  the  axis  of  the  orbit.  The  needle  is  then 
pushed  backward,  through  an  opening  in  the  extremity  of  the  central 


1  Sur  le  Plan  horizontal  de  la  Tete. 


PLANE  OF  THE  OPTIC  AXES. 


45 


branch,  passing  through  the  optic  foramen.  The  needle  does  not 
pass  through  the  center  of  this  foramen,  but  comes  in  contact  with 
its  upper  border. 

By  ascertaining  the  direction  of  the  needles  passing  through  both 
orbits,  in  relation  to  each  other  and  to  the  horizon,  the  plane  of  the 
axis  of  the  orbit  as  well  as  the  interorbital  angle  is  established. 

The  horizontal  plane  of  the  skull  is,  by  Broca,  arbitrarily  estab- 
lished as  the  plane  passing  from  the  lowest  border  of  the  alveola  of  the 
upper  jaw  backward  to  the  lowest  point  at  the  condyles  of  the  occipital 
bone. 


Fig.  12. — Stevens's  Craniostat  for  the  Examination  of  the  Planes  of  the 
Orbit.  The  triangular,  speculum-like  instrument  with  the  long  projecting 
needle  is  Broca's  instrument  for  ascertaining  the  direction  of  the  orbital 
axis. 

The  two  fixed  points  thus  chosen  are  convenient  for  the  craniolo- 
gist,  but  one  of  them  is  absolutely  useless  in  the  living  subject  and 
the  other  is  impracticable. 

The  points  selected  by  myself  as  fixed  points  to  indicate  the 
vertical  position  of  the  skull  are  the  ridge  or  elevation  between  the  two 
superciliary  ridges  (the  glabella)  and  the  concavity  just  below  the 
nasal  spine,  each  in  the  median  plane.  This  line  would,  in  most 
cases,  vary  a  few  degrees  from  a  right  angle  to  the  horizontal  line  of 
Broca,  but  it  is  as  liable  to  be  correctly  chosen  as  that  of  Broca,  is 
practicable  during  life,  and  is  essential  in  measurements  of  the  rota- 
tions of  the  eyes  made  by  the  tropometer. 

Fig.  12  shows  the  author's  method  of  placing  the  cranium  for  ex- 
amination of  the  planes  of  the  orbit. 


46  ANATOMY. 

Broca  finds  that  the  plane  of  the  optic  axis  varies  in  different 
skulls  to  the  extent  of  19°,  a  variation  which  corresponds  with  the 
variation  of  the  vertical  rotations  of  the  eyes  as  shown  by  the 
tropometer. 

It  has  been  shown  that  the  orbital  index  varies  with  the  type  of 
the  skull,  and  I  have  also  been  able  to  show  that  the  excursions  of  the 
eyes  of  the  living  subject  in  the  vertical  directions  vary  correspond- 
ingly to  the  type  of  the  orbit,  and  therefore  largely  corresponding  to 
the  type  of  the  cranium. 

Weiss  and  others  have  shown  that  the  breadth  of  the  orbital  open- 
ing compared  to  the  height  is  much  greater  in  infancy  than  in  adult 
life. 

The  cephalo-orbital  index  is  the  proportion  between  the  capacity 
of  the  cranium  and  that  of  the  orbit.  In  general,  it  may  be  stated  that 
the  index  is  about  27.  The  data  in  regard  to  different  races  is  not 
sufficient  to  make  this  index  an  important  element  of  distinction. 

The  smallest  distance  between  the  borders  of  the  two  orbits  is 
known  as  the  interorbital  distance. 

The  plane  which  occupies  the  space  between  the  orbital  borders 
of  either  orbit  is  known  as  the  base  of  the  orbit.  The  planes  or  bases 
of  the  two  orbits  deviate,  the  outer  border  of  each  toward  the  rear 
forming  an  angle  of  about  10°  or  15°  with  a  horizontal  line. 

These  bony  walls  do  not  by  any  means  adjust  themselves  to  the 
globular  forms  of  the  contained  globes,  but  between  the  ocular  globes 
and  the  orbital  walls  are  considerable  spaces,  narrowing  toward  the 
anterior  axes  of  the  orbits. 

ORBITAL  AXES  IN  ETHNOLOGY. 

We  are  not  in  possession  of  sufficient  data  to  venture  more  than 
the  suggestion  whether,  even  in  the  human  race,  there  may  not  have 
been  a  gradual  advance  toward  parallelism  of  the  optic  axes ;  whether 
the  orbital  axes  of  the  races  which  are  probably  the  most  primitive 
approach  in  this  respect  more  nearly  in  the  direction  of  the  lower 
species  than  to  the  more  advanced  races.  Ethnologists  who  have  given 
great  attention  to  the  "orbital  index"  have  supplied  us  with  scanty 
facts  in  regard  to  the  angles  of  the  orbital  axes.1 


1  The  value  of  the  orbital  angle  would  seem  to  be  worthy  of  a  greater 
degree  of  attention  than  it  has  received  from  ethnologists.  Broca  has  given 
some  data  from  which  it  appears  that  the  angle  formed  by  the  axes  of  the 
two  orbits  varies  in  man,  ranging  from  40°  to  50°,  while  in  the  monkey  tribe 


CONTENTS  OF  THE  ORBITS.  47 

CONTEXTS  OF  THE  ORBITS. 

Within  these  orbital  cavities  are  contained,  besides  the  ocular 
globes,  the  cushions  of  fatty  substance  and  loose  connective  tissue  which 
form  the  beds  in  which  the  eyes  rotate,  the  muscles  which  communicate 
the  movements  to  the  eyes  and  the  elevator  muscle  of  the  upper  lid,  the 
blood-vessels  and  nerves  which  supply  the  eyes,  muscles  and  other  con- 
tents of  the  orbit,  as  well  as  some  vessels  and  nerves  which  pass  to  the 
parts  beyond. 

The  ocular  portion  of  the  lachrymal  glands,  the  lachrymal  carun- 
cle, and  the  folds  of  conjunctiva,  the  pulley  of  the  tendon  of  the 
superior  oblique,  are  also  among  the  contents  of  the  orbits,  while  the 
capsule  of  Tenon,  considered  as  an  independent,  membrane,  forms  an 
investure  of  all  these  organs. 

If  the  muscles  are  carefully  separated  from  the  eyeball,  the  eye 
raised  in  such  a  manner  that  the  optic  nerve  may  be  severed  without 
injury  to  other  parts,  and  the  eye  removed  from  its  bed,  this  cushion 
is  seen  to  be  a  concave  half-sphere  with  surface  lubricous  and  smooth. 
The  lining  membrane  of  this  glistening  bed  is  formed  by  an  expansion 
of  the  capsule  of  Tenon,  a  membrane  which  not  only  serves  as  a  surface 
on  which  the  globe  of  the  eye  rests,  but  which  envelopes  the  tendinous 
insertions  of  the  muscles,  unites  them  with  each  other,  and,  as  we  shall 
see  as  we  discuss  its  character  more  in  detail,  forms  a  practical  aug- 
mentation of  the  extent  of  these  insertions  into  the  globe  of  the  eye, 
thus  in  practice  being  a  notable  element  in  the  surgical  treatment  of 
these  muscles. 

The  fatty  fibrous  cushion,  owing  to  the  conical  shape  of  the  bony 
cavity  and  the  extent  to  which  the  eye  fills  it  at  the  equator,  admits 
of  but  very  slight  compressibility,  as  it  is  easy  to  observe  by  pressing 
against  the  front  of  the  eyeball;  and  in  the  normal  condition  the 
pressure  of  the  cushion  behind  the  eye  is  not  augmented  in  such  a 
manner  as  to  modify  materially  the  action  of  the  muscles.  We  shall 
find,  however,  that  the  pressure  of  the  tissues  at  the  inner  side  of  the 


the  minimum  angle  is  33°  and  the  maximum  62°.  The  anthropoid  apes  have 
a  small  orbital  angle.  In  five  gorillas  the  angle  was  39.04°,  while  in  forty- 
three  men  the  average  angle  was  47.47°.  Among  lemurs  the  angle  was  raised 
to  73°.  Below  this,  in  the  scale  of  mammalian  life,  the  angle  greatly  increases, 
reaching  109.89°  in  the  horse  and  143°  in  the  rabbit.  Emmert  ("Auge  und 
Schildel")  made  measurements  of  the  angles  in  64  crania,  mostly  of  Swiss, 
but  did  not  carry  the  investigation  to  other  than  Europeans.  The  investiga- 
tions made  by  myself  have  been  confined  mostly  to  the  crania  of  those  who 
were  of  American  birth.  On  the  whole  the  data  are  meager. 


48  ANATOMY. 

eyeball  may  be  so  diminished  or  augmented  as  to  affect  to  a  certain 
extent  the  relative  tensions  of  the  motor  muscles;  and  the  same  may 
perhaps  be  said  of  modifying  influences  of  comparative  pressure  above 
and  below.,  at  or  in  advance  of  the  equator  of  the  eye.  Xevertheless, 
the  total  displacement  to  any  considerable  extent  of  the  eye  in  mass, 
from  side  to  side,  or  above  and  below,  is  not  permitted  by  the  bony 
walls  and  the  softer  environments,  in  the  normal  condition  of  the 
orbital  tissues. 

While  it  is  true  that  in  the  normal  condition  there  are  no  im- 
portant transient  changes  in  the  volume  of  the  cushion  against  which 
the  eye  rests,  and  in  which  it  performs  its  rotations,  under  certain  cir- 
cumstances of  disease  or  of  emaciation  the  amount  of  pressure  behind 
the  eye  may  be  materially  modified. 

So  also  by  an  unusual  tension  of  the  oblique  muscles  the  eyes  may 
be  forced  forward  so  as  to  assume  a  position  of  conspicuous  prominence, 
a  phenomenon  not  unusual  in  very  pronounced  declination. 

It  is  through  this  elastic  fatty  cushion  that  the  muscles,  vessels, 
and  nerves  of  the  eye  take  their  course,  that  of  the  recti  muscles  form- 
ing a  cone  with  the  apex  at  the  orbital  foramen  and  the  base  at  the 
equator  of  the  eye. 

This  orbital  tissue  is  formed  by  fatty  cells  enveloped  in  con- 
nective tissue  which  forms  a  network  which  surrounds  each  fat  cell, 
and  then  uniting  in  strong  trabecula3  divides  the  mass  of  cells  into 
separate  groups  or  lobules,  to  each  of  which  group  is  supplied  its 
branches  of  vessels. 

The  character  of  the  fat  varies  with  its  position.  That  imme- 
diately surrounding  the  capsule  which  envelopes  the  eyeball  and  also 
that  surrounding  the  optic  nerve,  is  extremely  fine,  the  fat  cells  being 
held  in  a  very  loose  mesh  of  connective  tissue,  thus  forming  a  bed  in 
which  the  eye  moves  with  the  least  possible  resistance.  In  other  parts 
of  the  orbit  the  fatty  tissue  is  more  firm  and  affords  support  for  the 
muscles  which  traverse  it. 

SECTION  IV. 

THE  MUSCLES. 

The  movements  of  the  eye  are  communicated  through  the 
influence  of  six  ribbon-like  muscles  which  find  a  lodgment  within  the 
orbit.  These  are  the  four  recti  and  the  two  oblique  muscles. 

With  the  exception  of  the  inferior  oblique,  all  these  muscles  have 


MOTOR  MUSCLES  OF  THE  EYES. 


49 


their  origin  at  the  optic  foramen.  Here  the  orbital  periosteum  forms, 
at  the  apex  of  the  orbit,  a  strong  fibrous  ring,  the  circle  of  Zinn,  which 
surrounds  and  forms  a  channel  for  the  passage  of  the  optic  nerve, 
while  it  affords  an  unyielding  support  for  the  tendinous  origin  of 
these  five  long  muscles,  as  well  as  that  of  the  elevator  of  the  upper 
eyelid.  From  this  point  of  support,  they  extend  forward,  in  grad- 
ually diverging  directions,  until  they  pass  the  equator  of  the  eye, 
to  the  places  where  the  four  recti  find  their  insertion  directly  upon 
the  surface  of  the  globe;  while  the  superior  oblique  proceeds  in  an 
indirect  manner  toward  a  similar  insertion  somewhat  behind  the 
equator. 


Fig.  13. — The  Motor  Muscles  of  the  Eyes.     (Drawing  by  the  Author.) 

Schwalbe's  scheme  of  a  section  through  the  posterior  extremities 
of  the  muscles  is  represented  in  the  accompanying  diagram.  (Fig.  14.) 

It  will  be  seen  that  the  superior  oblique  and  a  fasciculus  from 
the  external  rectus  find  their  origin  somewhat  removed  from  the 
circle  of  the  recti  terminating  the  pyramid  of  the  four  straight 
muscles. 

Within  the  circle  of  insertions  are  the  passages  of  the  naso-ciliary 
branch  of  the  ophthalmic,  the  common  oculo-motor  (III)  and  the 
abducens  (VI)  nerves. 

Below  the  circle  no  nerves  traverse  the  sphenoidal  fissure. 

At  about  8  to  10  millimeters  from  the  circle  of  Zinn,  the  tendons 
become  changed  into  muscles,  which  again  become  tendinous  before 
reaching  the  points  of  insertion  into  the  eyeball.  According  to  the 


50  ANATOMY. 

researches  of  Fuchs1  and  others  the  locality  of  the  insertions  varies 
considerably,  and  this  variability  is  especially  noticeable  in  the  muscles 
acting  vertically. 

THE  INTERNAL  KECTUS. 

(Synonyms:      Musculus  medialis,  M.  adducens.) 

The  origin  of  the  internal  rectus  is  at  the  circle  of  Zinn,  but  a 
tendinous  fasciculus  also  arises  further  back  from  the  sheath  of  the 
optic  nerve.  Passing  forward  nearly  parallel  to  the  inner  wall  of  the 
orbit,  it  comes  in  contact  with  the  eyeball  at  the  equator,  and  continues 
its  contact  until  it  emerges  from  the  capsule  of  Tenon  to  be  inserted 


Fig.  14. — Schwalbe's  Scheme  of  the  Origin  of  the  Eye  Muscles  at  the 
Posterior  Portion  of  the  Orbit  of  the  Right  Eye.  (From  Schwalbe,  "Lehr- 
buch  der  Anatomie  des  Auges,"  p.  227.)  II,  Optic  nerve.  Ill,  Oculomotor 
nerve.  IV,  Trochlear  nerve.  Vo,  Naso-ciliary  branch  of  ophthalmic  nerve. 
V6c,  Ophthalmic  branches  of  lachrymal  and  frontal  nerves,  VI,  Abducens 
nerve.  Ip,  Levator  palpebrse  superior  muscle,  os,  Superior  oblique,  rs, 
Superior  rectus.  rm,  Internal  rectus.  ri,  Inferior  reetus.  rl,  External 
rectus. 

into  the  eyeball  at  a  distance  of  about  8.8  millimeters  behind  the 
border  of  the  cornea.  Its  insertion  is  usually  either  a  straight  line 
or  forms  a  slight  curve  with  the  convexity  forward. 

The  internal  rectus  is  next  to  the  longest  and  is  the  strongest 
of  the  recti  muscles.  It  is  about  41  millimeters  in  length,  weighs, 
according  to  Volkmann,  %  gram,  and  its  tendon  insertion  into  the 
eyeball  is  10.3  millimeters  long.  This,  however,  is  subject  to  con- 
siderable variation.  The  variations  in  the  length  and  position  of  the 
insertion  will  be  discussed  further  on. 


'Graefe's  Arch./'  B.  xxx,  Abtheilung  iv,  pp.  1-60. 


MOTOR  MUSCLES  OF  THE  EYES.  51 

THE  EXTERNAL  RECTUS. 
(Synonyms:      Musculus  lateralis,  M.  abducens.) 

The  second  strongest  and  third  in  length  of  the  recti  muscles 
arises  by  two  fasciculi,  one  from  the  zonula  of  Zinn — the  inferior — and 
one — the  superior — from  the  fibrous  sheath  of  the  third  nerve  (Sap- 
pey).  Passing  forward  nearly  parallel  to  the  outer  orbital  wall,  it 
rounds  the  globe  of  the  eye  at  the  equator,  to  be  inserted  into  the  sclera 
about  7  millimeters  distant  from  the  border  of  the  cornea.  Its  length 
is  40.6  millimeters,  its  weight  7/10  gram,  and  the  extent  of  the  tendi- 
nous insertion  9.2  millimeters.  Like  the  insertion  of  the  internus  it 
is  nearly  straight.  From  its  sheath  it  sends  a  strong  fasciculus  to  be 
inserted  at  the  external  angle  of  the  orbit. 

THE  SUPERIOR  RECTUS. 

(Synonyms:      Musculus  attolens;    M.  levator  oculi.) 

The  rectus  superior,  the  weakest  and  longest  of  the  group,  has  its 
origin  at  the  upper  and  outer  part  of  the  zonula  of  Zinn  and  at  the 
border  of  the  sphenoidal  fissure.  Traversing  the  long  diameter  of  the 
orbit,  and  rising  at  an  angle  equal  to  that  of  the  arcade,  it  turns  upon 
the  eyeball  at  the  equator  and  passes  forward  to  be  inserted  at  about 
7.7  millimeters  above  and  behind  the  border  of  the  cornea,  nearly  at 
the  median  line.  Its  length  is  stated  at  41.8  millimeters  and  its 
weight  is  about  %  gram.  The  length  of  its  tendinous  insertion  is 
greater  than  that  of  the  other  recti,  being  on  the  average,  10.6  milli- 
meters. The  insertion  forms  a  stronger  curve  than  either  of  the 
laterally  acting  muscles,  and  sometimes  the  ends  curve  strongly  back- 
ward. In  some  cases  the  insertion  has  the  appearance  of  a  swallow's 
wings,  and  in  other  cases  it  is  an  irregular  wavy  line. 

The  capsular  sheath  of  the  superior  rectus  is  so  closely  united  by 
fibrous  bands  to  the  sheath  of  the  elevator  muscle  of  the  upper  lid  that 
the  action  of  these  two  muscles  is  in  a  measure  associated. 

THE  INFERIOR  RECTUS. 

(Synonyms:      Musculus  deprimens;    M.  humilis.) 

The  inferior  rectus,  arising  from  the  zonula  of  Zinn,  by  a  tendon 
in  common  with  the  internal  rectus,  extends  along  the  lower  border 
of  the  orbit,  and,  like  the  other  recti  muscles,  turns  upon  the  globe 


52  ANATOMY. 

of  the  eye  and  is  inserted  below  and  behind  the  cornea,  at  a  distance 
of  G.5  millimeters,  by  an  expansion  of  its  tendon  9.8  millimeters  in 
extent.  It  is  40  millimeters  long,  and  weighs  2/s  gram.  Its  insertion 
is  like  that  of  the  superior  rectus,  curved  with  the  convexity  forward. 
It  occupies  a  position  such  that  the  horizontal  meridian  of  the  eyeball 
would  divide  the  insertion  into  two  unequal  parts,  the  greater  being 
at  the  nasal  side. 

As  the  capsular  sheath  of  the  superior  rectus  is  intimately  con- 
nected by  fibrous  bands  to  the  sheath  of  the  elevator  muscle  of  the  lid, 
so  the  sheath  of  the  inferior  rectus  sends  bands  to  the  cul-de-sac  of  the 
conjunctiva  and  to  the  cartilage  of  the  lower  lid. 

The  numbers  above  given,  representing  the  length,  breadth, 
weight,  etc.,  are  those  given  by  Volkmann  and  other  authorities,  and 
are,  of  course,  approximate  onty  for  the  adult,  and  must  of  necessity 
vary  according  to  the  age  and  size  of  the  individual,  and  it  will  also 
be  seen  that  variations  result  from  the  axial  length  of  the  eye,  being 
thus  associated  with  the  refractive  conditions  and  with  the  direction 
of  the  axis  of  the  orbit,  and  that  there  are  many  normal  variations. 
But  while  the  comparative  relations  of  size  and  strength  will  remain 
nearly  in  the  proportion  given,  the  rotatory  influence  of  each  muscle 
must  be  to  a  certain  extent  determined  by  the  position  of  the  inser- 
tions. 

THE  SUPERIOR  OBLIQUE  MUSCLE. 

(Synonyms:      Musculus  oblique  major;    M.  oblique  longus.) 

The  superior  oblique,  arising  from  the  zonula  of  Zinn,  between 
the  origin  of  the  rectus  internus  and  the  superior  rectus,  has  its  course 
forward  and  inward  toward  the  superior  internal  angle  of  the  orbit, 
where  it  is  transformed  into  a  round  tendon  which  passes  through  a 
tendinous  pulley,  the  trochlea. 

This  fibrous  extension  of  the  periosteum  (the  trochlea)  is  situated 
at  the  trochlear  fossa  of  the  frontal  bone,  and  is  lined  by  a  synovial 
membrane. 

From  the  trochlea  the  tendon  changes  its  direction,  passing  out- 
ward, downward  and  backward,  forming  an  ang'e  with  its  former 
direction  of  about  50°,  expanding  again  into  a  flattened  fusiform  band 
which  passes  upon  the  upper  surface  of  the  bulb  between  the  eyeball 
and  the  superior  rectus,  beyond  the  equator  of  the  eye  in  its  course 
backward  and  outward  to  the  posterior  half  of  the  upper  surface  of  the 
globe,  and  mostly  outside  the  median  line.  Its  insertion  is,  therefore, 


MOTOR  MUSCLES  OF  THE  EYES.  53 

mostly  at  the  upper,  outer,  posterior  quadrant  of  the  eye,  attached 
obliquely,  with  its  upper  or  posterior  extremity  more  toward  the 
median  line,  encroaching  upon  this  and  in  many  cases  crossing  it, 
the  lower  extremity  finding  its  attachment  more  externally.  Divid- 
ing the  hall  by  the  equator  and  by  a  vertical  median  meridian,  a  small 
portion  of  the  tendinous  insertion  is  found,  in  hypermetropic  and  in 
certain  emmetropic  eyes,  at  the  upper  posterior  and  inner  quadrant  as 
above  remarked,  while  much  the  more  extensive  part  of  this  insertion 
is  in  the  upper,  posterior,  and  outer  quadrant  of  the  sclerotic  surface. 
In  emmetropic  and  myopic  eyes,  the  insertion  upon  the  outer  quadrant 
is  more  general  (Fuchs). 

If  we  examine  Fig.  16  we  see  that  the  insertion  is,  like  that  of  the 
other  long  muscles,  varied,  and  that  not  -only  the  position  of  the 
insertion  but  its  length  and  curvature  are  subject  to  variations. 

The  diagram  shows  also  that  the  anterior  extremity  extends  out- 
ward about  as  far  as  the  outer  extremity  of  the  external  reci^g,/^and~ 
that  it  forms  with  a  line  drawn  parallel  to  the  horizontal  meridian  and 
at  the  upper  border  of  the  cornea,  an  angle  of  about  45°  (Fuchs).1 
The  antero-external  extremity  approaches  very  near  to  the  posterior 
external  extremity  of  the  rectus,  so  near  indeed  that  the  capsular  in- 
vestment of  the  two  muscles  is  often  joined,  giving  the  insertions  the 
appearance  of  being  continuous.  Fuchs  found  in  a  single  instance 
that  the  tendons  themselves  were  actually  continuous.  The  diagram 
shows  also  the  curving  of  the  insertion  with  the  convexity  of  the 
curve  outward  and  backward.  Weiss  finds  the  average  length  of  the 
insertion  7.26  millimeters,  ranging  from  5.5  millimeters  to  9.75 
millimeters. 

THE  INFERIOR  OBLIQUE. 

(Synonyms:      Musculus  oblique  minor;    M.  oblique  brevis.) 

Of  all  the  muscles  which  communicate  motion  to  the  eyes,  the 
inferior  oblique  alone  does  not  find  its  origin  in  the  posterior  part  of 
the  orbit.  Arising  from  a  depression  in  the  orbital  plate  of  the  supe- 
rior maxillary  bone,  at  the  inferior  and  internal  angle  of  the  orbit  and 
just  within  the  border  of  the  cavity,  its  course  is  backward  and  out- 
ward, passing  just  between  the  orbital  wall  and  the  inferior  rectus, 
then  between  the  globe  of  the  eye  and  the  external  rectus  muscles,  to 


1  According  to  Weiss,  "Wachstum  des  Menschlichen  Auges,"  from  30°  to 
62°. 


54  ANATOMY. 

the  superior  external  and  posterior  quadrant  of  the  globe,  where  it 
finds  its  insertion  by  a  broad  aponeurosis  into  the  sclera,  nearly  facing, 
but  somewhat  behind,  the  insertion  of  the  superior  oblique.  In  its 
course,  as  it  hugs  the  globe  of  the  eye,  it  grows  gradually  wider  to- 
ward its  insertion,  which  is  more  nearly  horizontal  than  that  of  the 
superior  oblique.  According  to  Fuchs,  the  insertion  of  this  muscle  is 
the  most  variable  of  any  of  the  eye  muscles.  According  to  Weiss, 
the  length  of  the  insertion-line  varies  from  10.5  to  13  millimeters, 
averaging  11.45  millimeters.  In  general  the  line  of  the  insertion  is, 
at  the  extremity  nearest  the  cornea,  rather  above  the  lower  extremity 
of  the  insertion  of  the  external  rectus,  and  about  10  millimeters  ex- 
ternal to  that  insertion.  At  a  distance  varying  in  different  cases  it 
rises  obliquely,  passing  to  the  horizontal  meridian,  curving,  with  its 
convexity  upward.  The  inner  and  lower  portion  of  the  insertion  is 
more  irregular,  as  a  rule,  than  the  outer  and  upper  portion,  and  occa- 
sionally receives  one  or  two  small  bundles  of  tendons  from  a  partial 
insertion  line,  which  soon  unite  with  the  main  body  of  the  tendon.  A 
straight  line  drawn  from  the  two  extremities  of  the  insertion  would 
form  an  angle  with  the  horizontal  meridian  of  the  eyeball  varying 
from  16°  to  30°  (Weiss). 

SECTION  V. 

INSERTIONS  OF  THE  TENDONS. 

The  insertion  of  the  tendons  of  the  long  muscles  into  the  eyeball 
is  by  no  means  entirely  uniform  in  direction  in  different  eyes. 

In  less  than  half  of  the  cases  are  the  lines  of  insertion  of  the  in- 
ternal and  external  recti  so  placed  as  to  make  right  angles  with  the 
horizontal  meridan.  In  general,  when  either  does  not,  the  upper  end 
approaches  more  nearly  to  the  cornea.  On  the  contrary,  in  case  of  the 
external  rectus,  the  majority  of  insertions  have  the  upper  portion 
nearer  to  the  equator  than  the  lower  extremity. 

The  lines  of  insertion  of  the  rectus  superior  and  rectus  inferior 
have  their  outer  extremities  nearest  the  equator.  (Fig.  16,  p.  59.) 

In  their  relations  to  the  median  horizontal  meridian  the  inser- 
tions also  vary  by  being  placed  more  to  one  or  the  other  side  of  the 
meridian  line.  Thus  the  internal  and  external  rectus  in  about  half 
the  cases  have  the  middle  of  the  tendinous  line  coinciding  with  the 
horizontal  meridian,  while,  when  this  is  not  the  case,  the  middle  of 
the  insertion  of  the  internus  is  generally  below  the  horizontal  line, 


INSERTION  OF  THE  TENDONS.  55 

even  in  some  cases  to  the  extent  that  two-thirds  of  the  insertion  is 
below  the  meridian,  while  the  external  rectus,  on  the  contrary,  more 
frequently  varies  by  having  the  greater  part  of  its  insertion  line  above 
the  meridian. 

The  importance  of  such  irregularities  is  apparent;  for  while  the 
action  of  the  internus  in  such  cases,  if  at  all  extreme,  may  cause  a 
modification  of  the  declination  of  the  vertical  meridian,  the  com- 
parative distance  of  the  insertion  from  the  cornea  will  also  materially 
affect  the  action  of  the  muscle.  The  nearer  the  insertion  is  to  the 
cornea,  the  greater  will  be  the  influence,  ceteris  paribus,  in  rotating 
the  eye  in  the  direction  of  its  action. 

It  will  be  seen  from  what  has  preceded,  that  it  is  not  practicable 
to  form  a  table  of  exact  distances  of  insertion  from  the  cornea,  and 
that  such  tables  and  statements  must  be  accepted  only  as  approximate 
results  of  many  examinations. 

The  insertions  also  vary,  as  will  be  seen  by  the  diagram  at  page 
59,  in  length  and  direction.  It  is  not  to  be  assumed,  however,  that  a 
narrow  tendon  indicates  a  feebly  acting  muscle,  for  a  muscle  of  full 
rotating  capacity  may  have  a  narrow  insertion. 

It  should  be  remembered,  from  a  surgical  point  of  view,  that  the 
muscles  of  the  eye  have  what  may  be  regarded  as  a  double  insertion : 
that  directly  to  the  sclerotic,  and  that  formed  by  the  capsule. 

The  study  of  the  attachments  of  the  individual  muscles  to  the 
globe  of  the  eye,  is  of  primal  importance  to  the  surgeon.  The  exact 
extent  and  direction  of  each  insertion  has  an  important  bearing  upon 
the  rotations,  whether  by  a  single  muscle,  or  by  the  united  contractions 
of  more  than  one.  In  every  attempt  also  to,  modify  the  rotating  in- 
fluence to  any  exactly  graduated  extent,  either  by  relaxation  or  by 
contraction,  a  knowledge  of  the  extent  and  direction  of  the  insertion 
is  essential  to  the  highest  success. 

We  are  indebted  to  Fuchs1  for  a  most  careful  and  valuable  study  of 
the  comparative  locations  and  directions  of  the  insertions  of  the  various 


1"Beitra»e  Zur  Normalen  Anatomic  des  Augapfels;"  Archiv  fur  Oph., 
Bd.  xxx,  Abdth.  iv,  p.  1.  Only  in  recent  years  have  the  comparative  positions 
of  the  insertions  of  the  eye  muscles  been  studied.  Thus  Sommering  (1),  1791, 
and  Munz  (2),  1815,  state  that  the  insertions  of  the  four  recti  are  at  equal 
distances  from  the  cornea.  Somewhat  more  accurate  measurements  were 
given  by  Merkel  (3),  1820,  and  others,  and  in  1845  Rute  (4)  stated  the  insertion 
of  the  rectus  superior  to  be  7.2  millimeters,  of  the  rectus  inferior  68  milli- 
meters, of  the  rectus  internus  5.2  millimeters,  and  of  the  rectus  internus  7.5 
millimeters  from  the  corneal  border.  Ross  (5),  Hollsteen,  Piltz  (6),  Henle 
(7),  Hoffman  (8),  and  Merkel  (9)  gave  other  measurements  with  advancing 


56 


ANATOMY. 


muscles  attached  to  the  eyeball.  This  study,  undertaken  primarily  as 
a  topographical  investigation  bearing  upon  the  subject  of  myopia,  in- 
cludes incidentally  other  points  which  constitute  valuable  contributions 
to  this  subject. 

Although  the  refraction  of  the  eyes  used  as  material  in  his  in- 
vestigations was  unknown,  the  author  estimated  it  from  the  length  of 
the  optical  axis  in  each  case.  From  this  estimate  he  divides  the  eyes 
employed  in  the  investigation  into  emmetropic,  myopic,  and  hyper- 
metropic,  and  arrived  at  somewhat  different  results  according  to  .the 
assumed  refractive  conditions. 

The  following  table  gives  the  average  distances  of  the  insertions 
of  the  recti  muscles  into  the  globe  from  the  corneal  border,  as  found 
by  this  author: — 

Table  of  Measurements  of  the  Breadth  of  the  Insertion  Tendons  of  the  Recti  Muscles. — 

( From  Fuchs. ) 


31  EMMETROPIC  EYES 

20  MYOPIC  EYES 

4  HYPER- 
OPIC  EYES. 

Max. 

Min. 

Average 

Max. 

Min. 

Average 

Total 
Average 

Rectus  interims   .    . 

12.0 

8.8 

103 

13.7 

9.8 

11.4 

10.2 

"       extern  us  .    . 

10.2 

8.5 

9.2 

12.7 

8.8 

10.1 

9.1 

"       superior    .    . 
"       inferior  .  .    . 

13.2 
13.2 

8.5 

7.8 

10.6 
9.8 

12.7 
13.2 

9.0 

8.8 

10.9 
10.4 

9.9 
9.6 

The  findings  of  Weiss1  for  the  measurements  of  the  breadth  of 
the  insertions  of  the  recti  were  an  average  for  adults: — 

For  the  internal  rectus,  10.76.  (Max.,  12.5.     Min.,  10.) 

For  the  superior  rectus,  10.75.  (Max.,  11.25.      Min.,  10.) 

For  the  inferior  rectus,  10.35.  (Max.,  11.10.      Min.,  10.) 

For  the  external  rectus,  9.67.  (Max.,  12.0.       Min.,  8.3) 


completeness.      See  Weiss;    "Uber  das  Wachstum  des  Menschlichen  Auges," 
for  more  lengthy  details. 

(1)  "Muskellehre,"  1791. 

(2)  Martin  Munz:     "Handbuch  der  Anatomic,"  1825. 

(3)  "Anatomie,"   1820. 

(4)  "Lehrbuch   d'Ophthalmologie,"   1845. 

(5)  "Chirurg.  Anatomy,"  1848. 

(6)  "Augenheilkunde,"  1859. 

(7)  Henle:     "Handbuch  d'Anatomie,"  1866. 

(8)  "Anatomie,"  1872. 

(9)  Graefe  und  Samisch. 

Leopold  Weiss,  "Uber  des  Wachstum  des  Menschlichen  Auges,"  1897. 


INSERTION  OF  THE  TENDONS. 


57 


Eight  Eye  of  Six  Year  Old  Child. 


Above. 


Below. 


Inner  Side. 


Outer  Side. 


Above. 


Left  Eye  of   Girl  Thirteen  Years  Old. 


Below. 


Inner  Side. 


Outer  Side. 


Right  Eye.     Known   to  Have  Been  Emmetropic. 


Below. 


Inner  Side. 


Outer  Side. 


Fig.  15. — Diagrams  Indicating  the  Insertions  of  the  Muscles  in  Three  Pairs 
of  Eyes  of  Young  Persons.  (From  "Wachstum  des  Menschlichen  Auges." 
Used  by  permission  of  Professor  Weiss.) 


The  table  on  following  page  gives  the  distances  of  the  insertions 
of  the  recti  muscles  into  the  globe  from  the  corneal  border  as  found 
by  Fuchs.1 


r"Beitrage   Zur  Normalen   Anatomie  des   Augapfels;"   Archiv   fur   Oph., 
Bd.  xxx,  Abdth.  iv,  p.  1. 


58 


ANATOMY. 


Table  of  Distances  of  the  Insertions  of  the  Muscles  from  the  Cornea. —  From  Fuchs.) 


4  HYPER- 

31  EMMETROPIC  EYES 

20  MYOPIC  EYES 

OPIC  EYES 

DistJ  from  Border 

Dist.  from  Border 

From 

Border 

Max. 

Min. 

Average 

Max. 

Min 

Average 

Average 

Eectus  internus    .    . 

6.7 

4.3 

5.5 

6.2 

48 

5.5 

5.2 

"      inferior  .    .    . 

8.2 

5.3 

6.5 

8.5 

6.3 

6  9 

6.0 

"      externus 

8.2 

5.3 

6.9 

8.2 

5.8 

6.9 

64 

'  '     superior  .   .    . 

9.0 

6.8 

7.7 

9.7 

6.3 

7.7 

7.1 

It  is  readily  seen  from  the  differences  of  the  figures  for  the 
maximum  and  minimum  that  the  individual  variations  are  consider- 
able. But  not  only  are  these  variations  in  the  distance  of  the  inser- 
tions of  the  tendons  of  the  individual  muscles  from  the  cornea,  the 
direction  of  the  attachment  and  its  length  are  different  for  different 
eyes.1 

In  the  new-born,  the  measurements  were : — 


Average  for  the  rectus  internus,  3.6  mm. 
Average  for  the  rectus  externus,  4.9  mm. 
Average  for  the  rectus  inferior,  5.0  mm. 
Average  for  the  rectus  superior,  5.8  mm. 

In  adult  cases: — 

Average  for  the  rectus  internus,  5.85  mm. 
Average  for  the  rectus  externus,  6.75  mm. 
Average  for  the  rectus  inferior,  6.85  mm. 
Average  for  the  rectus  superior,  8.01  mm. 


(Max.,  4.3.  Min.,  3.0.) 

(Max.,  5.5.  Min.,  4.0.) 

(Max.,  5.5.  Min.,  4.0.) 

(Max.,  7.0.  Min.,  5.0.) 


(Max.,  6.75.  Min.,  5.0.) 

(Max.,  7.75.  Min.,  6.25.) 

(Max.,  7.5.  Min.,  6.0.) 

(Max.,  9.0.  Min.,  6.75.) 


Although  the  rule  was  found  to  prevail  that  when  the  distance 
from  the  cornea  of  a  tendon  insertion  is  greater  or  less  than  normal  the 
insertion  of  the  other  tendons  is  similar,  and  that  thus  the  comparative 
arrangement  for  an  individual  eye  is  in  most  cases  subject  to  the 
general  plan,  this  rule  was  by  no  means  constant.  In  case  of  the 
relations  between  the  rectus  externus  and  rectus  inferior  the  variations 
are  sometimes  extreme. 

The  results  of  the  very  careful  measurements  were  in  each  case 
represented  upon  a  diagram  in  which  a  line  indicated  the  exact  length 


1  Leopold  Weiss  ("Uber  das  Wachstum  des  Menschlichen  Auges,"  etc.) 
found  marked  differences  in  the  distances  of  the  insertions  of  the  recti  muscles 
from  the  border  of  the  cornea.  That  of  the  superior  rectus  was,  however, 
greatest,  and  the  internal  rectus  the  least. 


INSERTION  OF  THE  TENDONS. 


59 


of  the  insertion  and  its  relations  to  the  cornea  and  equator  magnified 
four  times.  The  majority  of  the  measurements  were  drawn  upon  the 
same  paper. 

Thus  the  diagrams  enable  one  to  compare  the  variations  in  the 
insertions  of  the  individual  muscles.      All  these  diagrams  were  drawn 


Fig.  16. — Design  by  the  Author  to  Indicate  the  Relative  Insertions  of  the 
Different  Muscles  into  the  Sclera  (according  to  the  data  supplied  by  Pro- 
fessor Fuchs).  S.O.,  Superior  oblique.  8.R.,  Superior  rectus.  I.O.,  In- 
ferior oblique.  Ex.R.,  External  rectus. 

upon  a  projection  plane  in  which  straight  lines  replaced  the  curves  of 
the  cornea  and  equator. 

In  order  to  present  in  much  less  space  and  in  a  manner  somewhat 
more  readily  comprehended  the  results  arrived  at  by  this  investigation, 
I  have  in  the  accompanying  figure  attempted  to  reproduce  these  dia- 
grams in  a  combined  form,  reducing  at  the  same  time  the  enlarge- 
ment from  four  times  to  rather  less  than  twice  the  length.  If  I  have 
not  fully  succeeded,  I  have  at  least  represented  graphically  the  gen- 


60  ANATOMY. 

oral  fact  of  these  variations.  In  the  figure  the  larger  circle  represents 
the  equator  of  the  eye,  the  smaller  the  cornea.  The  vertical  line  rep- 
resents the  vertical  meridian,  and  the  horizontal  the  horizontal  meri- 
dian. On  the  left  side  are  shown  the  lines  representing  the  insertions 
of  the  internal  recti  of  nine  eyes  assumed  to  be  emmetropic;  on  the 
right  the  insertions  of  the  external  recti  of  the  same  series  of  eyes; 
on  the  vertical  line  are  superior  and  inferior  recti,  and  assuming  a 
more  oblique  direction  are  those  of  the  superior  and  inferior  oblique, 
the  first  on  the  vertical,  the  second  on  the  horizontal  line. 

It  requires  no  long  study  of  the  lines  in  this  diagram  to  learn  that 
not  only  are  the  insertions  of  the  muscles  of  different  lengths,  but  that 
they  are  inserted  at  different  angles  with  the  border  of  the  cornea,  and 
that  the  distances  between  the  corneal  border  and  the  insertions  vary 
materially ;  and  we  may  well  adopt  the  conclusion  of  the  author  that, 
"from  the  above  facts  it  would  seem  not  improbable  that  changes  in 
the  relations  of  the  insertion  distances  should  have  the  result  of  a 
disturbance  in  the  muscular  balances."  From  this  very  reasonable 
deduction,  however,  the  learned  investigator  soon  escapes,  for  ap- 
parent difficulties  arise  which  lead  him  to  a  different  conclusion.  The 
fact  that  the  greater  number  of  deviations  of  the  eyes  as  they  have  been 
commonly  observed  appear  to  him  to  be  in  the  lateral  direction  and  not 
in  the  vertical,  leads  him  to  say:  "We  are  not  to  attribute  too  much 
meaning  to  these  variations  of  insertion  distance;  we  observe  the  same 
things  with  respect  to  the  rectus  superior  and  rectus  inferior"  The 
relations  of  the  insertions  of  these  two  muscles  are  in  fact  very  variable 
and  they  are  frequently  found  entirely  different  in  the  two  eyes  belong- 
ing to  the  same  person.  Indeed,  he  might  have  made  this  statement 
regarding  variations  still  stronger  by  giving  the  actual  results. 

This  declaration  that  we  must  abandon  a  legitimate  conclusion 
because  it  does  not  harmonize  with  apparent  and  conventionally  recog- 
nized phenomena  is  based  upon  the  almost  universally  superficial  obser- 
vations in  regard  to  the  ordinary  forms  of  strabismus.  And  the 
further  statement  of  the  author  that  "disturbances  of  these  (vertically 
acting)  muscles  are  however  only  rarely  met  with/'  may  be  easily 
shown  to  be  erroneous  by  examinations  with  the  tropometer.  I  have 
shown1  that  the  lateral  deviations  of  strabismus  (strabismus  divergens 
and  strabismus  convergens)  are  very  frequently  the  result  of  vertical 


1  Annales  d'Oculistique,  April,  1895.      I  had  previously  shown  that  hyper- 
phoria  is  frequently  the  inducing  cause  of  lateral  deviations. 


CAPSULE  OF  TENON.  61 

tensions,  and  in  the  course  of  this  work  it  will  be  seen  that  such 
vertical  tensions  combined  with  the  declinations  due  to  the  manner  in 
which  the  tendons  are  inserted  into  the  sclera  are  most  commonly  the 
cause  of  the  lateral  deviations.  From  the  table  found  in  the  section 
on  "Strabismus,"  it  will  also  be  seen  that  cases  of  vertical  deviations 
are  quite  as  common  as  lateral. 

The  position  of  the  insertion  line  of  the  four  recti  muscles  in 
respect  to  the  meridian  line  and  the  equator  is  seen  by  the  diagram  to 
be  subject  to  many  irregularities.  Commencing  with  the  insertions  of 
the  outer  and  inner  muscles  it  will  be  observed  that  in  about  one-half 
the  cases  the  horizontal  meridian  cuts  the  insertion  in  the  middle.  In 
general,  when  this  is  the  case,  the  insertions  usually  extend  below 
rather  than  above  this  symmetrical  position.  In  some  cases  nearly 
two-thirds  lies  below  the  horizontal  meridian.  In  respect  to  the 
external  rectus,  while  about  the  same  proportion  of  the  insertions  are 
cut  by  the  horizontal  meridian,  the  variations  are  more  frequently 
above  than  below  that  meridian,  and  these  variations  are  frequently  of 
high  grade. 

In  less  than  half  the  cases  are  the  insertion  lines  found  at  right 
angles  with  the  horizontal  meridian ;  while  the  upper  extremity  of  the 
internus  oftenest  lies  nearest  the  cornea,  the  reverse  is  true  of  the 
externus. 

In  the  largest  proportion  of  cases  the  tendon  of  the  rectus 
superior  has  its  longest  part  outside  the  vertical  meridian.  The 
displacement  of  the  inferior  rectus  insertion  is  often  outward,  but  to  a 
less  extent.  The  inner  border  of  each  of  these  lies  nearer  to  the 
cornea  than  the  outer.  As  a  rule,  this  obliquity  is  quite  marked. 


SECTION  VI. 

THE  CAPSULE  OF  TENON  OR  ORBITO-OCULAR  APONEUROSIS. 
(Synonyms:  "Fascia  Tenoni;  F.  albuginea  bulbi;  Tunica  vaginalis  bulbi.) 

As  has  already  been  stated,  much  of  the  space  of  the  orbit  is 
filled  by  fatty  material  enclosed  in  a  network  of  loose  fibrous  tissue. 
This  fibrous  tissue  is  closely  connected  with  the  periosteum  and  may 
be  regarded  as  a  modification  of  this  membrane.  In  certain  positions 
this  fibrous  tissue  assumes  the  character  of  a  well-defined  membrane 
which  serves  as  an  investment  of  the  eyeball  and  of  the  tendons  of 
the  muscles  within  the  orbit. 


62 


ANATOMY. 


HISTORICAL  NOTE  ON  THE  CAPSULE  OF  TEXOX. 

Realdus  Columbus,  whose  writings  appeared  about  the  middle  of 
the  16th  century,  a  friend  of  Vesalius,  and  an  anatomist  distinguished 
for  his  great  erudition  and  accuracy  in  research,  for  whom  is  claimed 
the  honor  of  the  discovery  of  the  stapes  (an  honor,  however,  awarded 
by  Fallopius  to  Ingrassias),  described  what  is  now  known  as  the  cap- 
sule of  Tenon  under  the  name  tunica  innominaia,  and  claimed  to 
have  discovered  this  membrane.  It  had,  however,  probably  been 
•described  by  Galen  under  the  name  of  tunica  sexta.  But  the  knowl- 


Fig.  17. — Diagram  Indicating  the  Arrangement  of  the  Capsule  of  Tenon, 
from  a  Side  View.  The  narrow  carmine  lines  represent  the  positions  of  the 
capsule.  (Drawing  by  the  Author.) 

edge  possessed  by  Galen,  Columbus,  and  others  who  followed  them 
was,  concerning  the  actual  extent  and  character  of  the  membrane, 
extremely  vague.  It  remained  for  the  French  anatomist  Tenon  to 
describe  the  capsule  in  its  various  modifications  and  relations  to  the 
organs  within  the  orbit.1 

Tenon  called  attention  to  the  difficulties  which  at  his  time  sur- 
rounded the  investigation  of  the  subject,  but  showed  that  the  apo- 
neurosis  was  common  to  the  optic  nerve,  to  the  globe  of  the  eye,  and 
to  the  eyelids;  that  it  constituted  an  extension  of  the  insertion  of 
the  tendons  of  the  motor  muscles ;  and  that  it  sent  out  strong  bands 
which  connected  the  eyeball  with  the  orbit. 

1  Tenon:  "Memoires  et  d'Observations  sur  1'Anatomie,  la  Pathologic  et 
la  Chirurgie,  et  Principalement  sur  POrgane  de  1'Oeil,"  p.  193.  Paris,  1806. 


CAPSULE  OF  TENON.  63 

Like  many  another  discovery  in  science,  this  remarkable  expo- 
sition was  forgotten  through  many  years,  and  it  was  only  after  the 
discovery  of  strabotomy  by  Stromeyer  in  1839,  when  questions  rela- 
tive to  the  contents  of  the  orbit  assumed  a  new  interest,  that  the 
observations  of  Tenon  were  revived  and  their  importance  compre- 
hended. 

Much  has  since  then  been  added  to  the  knowledge  of  this  tunic 
through  the  researches  of  later  anatomists,  but  the  honor  of  the  first 
systematic  description  rests  with  Tenon. 

In  regard  to  some  of  the  subsequent  discoveries,  Bonnet1  says: 
"Tenon  discovered  the  existence  of  this  capsule.  .  .  .  M.  Mal- 
gaigne  insisted  more  than  Tenon  upon  the  part  of  the  capsule  which 
is  intermediary  to  the  conjunctiva  and  the  sclerotic.  M.  Baudrus 
found  the  sheaths  which  the  capsule  sends  to  the  recti  and  oblique 
muscles.  I  discovered  the  intimate  adherances  of  the  muscles  with 
their  sheaths  and  with  the  capsule." 

In  this  Bonnet  gives  scant  credit  to  Lucien  Boyer  for  his  ob- 
servations upon  the  close  union  of  the  muscles  with  each  other  and 
to  the  eye  through  the  medium  of  the  capsule  and  its  extensions.2 

This  capsule  of  Tenon,  while  it  has  not  failed  to  be  recognized 
as  an  important  anatomical  factor  of  the  contents  of  the  orbit,  has 
not  been  sufficiently  considered  from  the  standpoint  of  conservative 
surgical  corrections  of  anomalous  tensions  of  the  eye  muscles.  Atten- 
tion has  been  called  more  especially  to  its  importance  as  an  accessory 
to  the  recti  muscles,  requiring  surgical  division  in  order  to  increase 
the  effect  of  the  tenotomy  of  the  tendon  of  the  muscle  itself,  rather 
than  to  its  office  in  maintaining  exact  and  physiological  relations 
between  the  muscle  tendon  and  the  eyeball,  not  only  in  the  normal 
state,  but  in  case  of  a  division  of  the  former.3 


1  Annal.  d'Oculistique,  1842,  p.  148. 

2  Gazette  des  Hopitaux,  1841. 

"Bonnet  first  called  attention  (Annales  d'Oculistique,  1841,  pages  27-30) 
to  the  fact  that  unless  the  capsular  extension  constituting  the  sheath  of  a 
tendon  was  divided  in  the  operation  for  strabismus,  the  muscle  might  continue 
to  act  as  before.  Hence,  if  the  incision  was  first  made  through  this  the 
"stilet  (then  used  instead  of  the  Jiook)  glides  without  obstacle  behind  the  sheath 
of  the  muscles,  and  one  may  cut  them  (the  muscles)  together  icith  their 
aponeuroses  surely  and  completely." 

The  more  recent  methods  of  introducing  a  hook  beneath  the  tendon  and 
behind  its  insertion,  and  bringing  the  extremity  out  at  the  other  side  of  the 
tendon,  thus  making  the  section  of  what  is  included,  results  practically  the 
same  as  the  complete  section  recommended  by  Bonnet.  It  also  effectually  de- 
stroys the  physiological  relation  of  the  tendon  to  the  eyeball  and  to  the 
neighboring  muscles. 


64  ANATOMY. 

While  it  is  true  that  some  reference  has  from  time  to  time  been 
made  to  the  importance  of  preserving,  in  some  measure,  the  capsular 
attachments,  the  actual  practice  has  been  to  sever  them. 

In  respect  to  the  importance  of  the  office  of  the  capsule  of  Tenon 
in  modifying  and  maintaining  the  effects  of  surgical  operations  upon 
the  eye  muscles,  the  views  advanced  and  maintained  by  myself  during 
a  number  of  years  are  in  contrast  with  the  views  previously  main- 
tained.1 

INTERNAL  OR  BULBAR  CAPSULE. 

The  eyeball  rests  in  this  portion  of  the  capsule  much  as  an  acorn 
lies  in  its  cup.  Commencing  at  the  point  where  the  connective  tissue 


Fig.  18. — Investment  of  the  Muscles  of  the  Eye  by  the  Capsule  of  Tenon. 
Reproduced  from  Motais's  "Anatomie  de  1'Appareil  Moteur  de  1'CEil,"  by 
the  kind  permission  of  Professor  Motais. 

is  condensed  into  a  membranous  ring  at  the  entrance  of  the  optic 
nerve  within  the  orbit,  we  may  trace  the  capsule  as  an  outer  sheath 
of  that  nerve  and  as  a  membrane  forming  the  lining  of  the  socket  in 
which  lies  the  greater  part  of  the  globe  of  the  eye.  The  surface  of 
this  bulbar  portion  of  the  capsule  facing  the  sclera  is  smooth  and 
covered  with  epithelium,2  thus  receiving  the  character  of  a  serous 
membrane.  It  is  closely  attached  to  the  sclera  around  the  entrance 
of  the  optic  nerve.  The  ciliary  nerves  and  short  ciliary  arteries  pene- 
trate _the  membrane  at  this  point  and  receive  an  investment  from  it. 
Further  forward  the  vasa  vorticosa  traverse  this  portion  of  the  mem- 

1  These  views  will  be  stated  in  the  sections  on  Heterophoria  and  Stra- 
bismus. 

2  Schwalbe :   "Lehrbuch  des  Anatomie  des  Auges." 


CAPSULE  OF  TENON.  65 

brane.  Behind  the  line  of  insertion  of  the  muscles  the  capsule  is 
reflected  backward  to  form  the  common  aponeurosis  of  the  group  of 
muscles  occupying  the  orbit.  It  is  called  also  the  external  capsule 
or  muscular  capsule.  It  invests  the  tendons  as  a  sheath  of  some 
thickness,  becoming  more  intimately  attached  to  the  surface  of  the 
muscles  and  thinner  as  it  extends  backward.  Between  the  muscles, 
it  extends  as  a  distinct  but  rather  thin  membrane  forming  a  con- 
tinuous structure. 

Posteriorly,  returning  to.  the  ring  from  which  the  long  muscles 
have  their  origin,  it  undergoes  histological  changes  and  unites  with 
or  assumes  the  form  of  the  periosteum. 

EXTERNAL  CAPSULE  OR  EXTERNAL  APONEUROSIS. 

Returning  now  to  the  line  where  the  bulbar  capsule  is  reflected 
as  the  common  aponeurosis  of  the  muscles,  we  find  the  portion  of  this 
structure  most  interesting  from  the  surgical  point  of  view.  In  text- 
books of  anatomy  and  ophthalmology  it  is  generally  stated  that  the 
tendons  of  the  muscles  "penetrate"  the  capsule  at  this  insertion. 
This  expression  conveys  an  incorrect  impression.  As  we  have  seen, 
the  capsule  is  reflected  back  upon  the  muscles.  In  the  general  line 
of  this  reflection,  it  extends  between  them  as  a  strong  band  and  from 
the  borders  of  the  tendons  the  sheath  spreads  out  in  such  a  manner 
as  to  give  the  appearance  of  a  greatly  extended  tendon.  To  render 
this  extension  more  important,  strong  bands  extend  from  the  angle 
of  reflection  to  unite  with  the  sclera,  thus  constituting  the  capsular 
extension  an  accessory  portion  of  the  tunica  of  much  importance. 

The  aponeurosis,  for  the  better  understanding  of  this  course, 
may  be  regarded  as  consisting  of  two  layers,  one  of  which  lines  the 
inner,  the  other  the  outer  surface  of  the  muscles;  the  two  being 
united  in  the  spaces  between  the  different  muscles.  The  reflection 
of  the  internal  of  these  layers  occurs  at  a  distance  of  several  milli- 
meters behind  the  insertion  of  the  muscle,  so  that  if  the  muscle  is 
raised  from  the  eyeball  (as  in  Fig.  19)  a  triangular  space  is  left, 
the  three  sides  being  formed  respectively  by  the  sclera,  the  tendon 
and  the  fold  of  the  capsule. 

As  the  muscle  is  raised,  the  membrane  is  seen  to  be  smooth, 
shining,  and  perfectly  continuous  upon  the  inner  surface  of  the 
muscle,  and  upon  the  surface  of  the  globe,  as  well  as  at  the  location 
of  the  fold. 


66  ANATOMY. 

The  external  layer  follows  the  tendon  closely,  but  leaves  it  at  its 
proximal  fifth,  and,  passing  forward,  becomes  closely  united  with  the 
sclera,  extending  nearly  to  the  cornea.  At  this  point  it  is  some- 
what difficult  to  separate  it  from  the  sclera  on  the  one  side,  and  the 
•conjunctiva  on  the  other. 

This  layer  while  resting  upon  the  muscle  and  tendon,  until  the 
latter  is  lost  in  the  sclera,  is  free  in  the  anterior  part  of  the  course 
•of  the  tendon.  The  layer  here  surrounds  the  eye  as  a  band  and  does 
not  consist  simply  of  fibers  radiating  from  the  tendons.  Anterior 
to  the  equator,  it  becomes  thickened  and  strengthened,  thus  forming, 
with  the  internal  layer,  a  double  sheath,  in  which  are  found  the  ten- 
dons of  all  the  motor  muscles  of  the  eye. 


Fig.  19.— 1,  Sclera.    2,  Tendon.    3,  Fold  of  the  capsule.    4,  External 
layer  of  the  capsule.     (Diagram  by  the  Author.) 

A  strong  layer,  dividing  from  this  external  layer  at  the  cul-de-sac 
of  the  conjunctiva,  passes  forward  beneath  the  conjunctiva  of  the 
lids,  and  this  layer  again  dividing,  sends  a  thick  and  strong  layer  to 
the  border  of  the  orbit. 

Still  another  important  reflection  from  this  portion  of  the  mem- 
brane is  that  which  covers  the  elevator  muscle  of  the  lid  and  again 
divides,  sending  a  layer  toward  the  margins  of  the  orbit,  where  it 
becomes  continuous  with  the  periosteum,  and  as  such  it  lines  the 
orbital  walls  and,  passing  backward,  completes  the  circle  of  the  ex- 
ternal layer  at  the  orbital  foramen.  At  various  parts  of  its  course, 
the  membrane  sends  off  layers  of  tissue  which  serve  as  envelopes  to 
"vessels  and  nerves  which  traverse  it,  and  other  more  delicate  layers 
which  surround  the  fatty  lobules  which  constitute  the  fatty  cushion 
of  the  orbit. 


LIGAMENTOUS  AILERONS.  67 

LlGAMENTOUS    AILERONS    OR    BRIDLES — ORBITAL    MUSCLES. 

("Gaines  Muscularis,"  C.  Sappey:  "Recherches  sur  Quelques  Muscles  a 
Fibres  Lisses,"  etc.,  18G7.  "Fasciae  Musculares  Oculi,''  etc.) 

Tenon  described  strong  bands  of  fibers  which  pass  from  the  sur- 
face of  the  sheath  of  the  internal  and  external  recti  to  the  orbital 
walls,  under  the  name  of  ligamentoiis  ailerons.  Sappey  found  that 
these  ailerons  contained  muscular  tissue  and  gave  to  them  the  name 
of  orbital  muscles.  Motais  finds  similar  bands,  but  wanting  muscle 
fibers,  extending  from  the  other  recti  muscles  and  from  the  lesser 
oblique.  These  ailerons  or  orbital  muscles  are,  in  fact,  modifications 
of  the  capsule,  containing  in  case  of  the  internus  and  externus  a  few 
muscular  fibers.  One  such  band  passes  from  the  superior  rectus  to 
the  tissues  connected  with  the  upper  eyelid,  and  may  impart  to  the 
lid  a  movement  associated  with  that  of  the  rectus.  Other  bands  con- 
nect the  superior  rectus  and  the  elevator  of  the  lids;  a  similar  fas- 
ciculus unites  the  inferior  rectus  and  inferior  tarsal  cartilage. 

Of  these  ailerons,  that  from  the  external  rectus  is  the  most  im- 
portant in  strength  and  extent.  Taking  its  origin  from  the  whole 
breadth  of  the  capsular  sheath  of  the  anterior  portion  of  the  external 
rectus,  it  is  condensed  into  a  conspicuous  band  which,  parting  from 
the  anterior  portion  of  the  muscle,  extends  to  the  external  angle  of 
the  orbit.  It  has,  according  to  Motais,  a  breadth  of  7  or  8  milli- 
meters, and  a  length,  from  its  commencement  on  the  sheath  of  the 
muscle  to  its  insertion  into  the  orbit,  of  18  to  20  millimeters.  Its 
thickness  varies  from  3  to  6  millimeters.  At  the  somewhat  extended 
region  of  its  origin,  the  sheath  becomes  very  firmly  attached  to  the 
muscle,  so  that  an  attempt  to  separate  the  capsular  investment  from 
the  muscle  results  in  tearing  the  latter.  Its  insertion  at  the  orbital 
border  is  about  6  or  7  millimeters  in  extent. 

The  aileron  from  the  internal  rectus,  though  less  thick  and  con- 
spicuous than  that  from  the  external  rectus,  is  still  easy  to  find.  Like 
the  origin  of  that  of  the  external  rectus,  the  inner  aileron  and  the 
sheath  at  the  locality  of  the  origin  is  very  intimately  connected  with 
the  muscle  through  a  space  of  6  or  7  millimeters  from  before  back- 
ward. Leaving  the  muscle  at  its  anterior  portion,  it  proceeds  to  the 
internal  angle  of  the  orbit,  where  it  is  inserted  into  the  os  unguis. 
Sappey  has  found  in  it  many  muscular  fibers,  especially  in  its  ante- 
rior extremity.  Fibers  which  pass  to  the  tarsal  cartilage  are  known 
as  Homer's  muscle  or  tensor  tarsi. 


68  ANATOMY. 

The  band  extending  from  the  superior  rectus  joins  the  sheath 
of  the  elevator  of  the  lid;  starting  from  about  as  far  back  as  the 
equator  of  the  eye,  it  attaches  itself  by  one  layer  to  the  elevator  mus- 
cle, being  reflected  back  upon  it,  while  another  layer  passes  to  the 
cartilage  of  the  upper  lid. 

The  aileron  from  the  inferior  rectus  forms  behind  the  equator 
of  the  eye  and  passing  forward  and  downward,  enveloping  the  inferior 
oblique,  finds  its  insertion  in  the  cartilage  of  the  lower  lid. 

The  inferior  oblique  muscle  sheath  sends  a  band  strongly  liga- 
mentous  downward  and  outward  and  forward,  having  a  muscular 
origin  of  7  or  8  millimeters  and  an  insertion  into  the  inferior  interior 
angle  of  the  orbit  of  about  5  or  6  millimeters.  The  union  of  this 
ligament  and  of  that  from  the  inferior  rectus  forms  a  support  to  the 
oblique,  somewhat  similar  to  a  pulley. 

These  fibrous  bands,  ailerons,  bridles,  orbital  muscles,  or  orbital 
tendons  as  they  are  called  may  act  as  bands  of  restraint,  preventing 
excessive  rotation  of  the  eyes  from  too  great  contraction  of  the  mus- 
cles. Not  only  may  these  bands  serve  as  means  of  restraint  to  exces- 
sive excursions  of  the  eyes,  they  may  also  serve  as  media  of  associa- 
tion of  action.  For  example,  between  the  superior  rectus  and  the 
elevator  of  the  lid  the  bands  may  assist  in  associating  the  elevating 
influence  of  the  two  muscles  which  act,  one  upon  the  eyeball,  and 
the  other  upon  the  lid,  which  must  be  raised  simultaneously  with  the 
eye,  in  order  that  the  pupil  may  remain  uncovered.  Between  the 
capsule  or  fascia  as  it  covers  the  upper  lid  and  the  skin  of  the  lid 
these  bands  are  again  conspicuous. 


GENERAL  CONSIDERATION  EEGARDING  THE  AILERONS  AND 

APONEUROSIS. 

It  is  easy  to  see  that  these  strong  bands  may  have  a  very  impor- 
tant influence  in  case  of  tenotomy  of  either  of  the  muscles  from 
which  they  take  their  origin. 

It  is  easy  also  to  observe  that  the  broad  insertion  of  the  capsule 
upon  the  sclera  near  the  cornea,  closely  enveloping  the  insertions  of 
the  recti  muscles  must  lend  important,  indeed,  essential,  support  to 
the  muscle,  in  case  the  tendinous  insertion  is  separated  from  the 
sclera. 

The  glistening  surface  of  the  inner  capsule  in  which  the  eye  rests 
strongly  suggests  the  rotation  of  the  eye  upon  this  smooth  surface, 


VESSELS  OF  THE  EYE  MUSCLES.  69 

as  the  head  of  the  femur  rotates  in  its  socket.  And  this  is  the  inter- 
pretation almost  universally  given  by  authors. 

The  fact,  however,  of  the  close  adhesion  of  the  capsule  around 
the  scleral  entrance  of  the  optic  nerve  and  that  of  its  firm  insertion 
around  the  eye  near  the  cornea,  appear  to  render  such  movement  of 
a  very  limited  character.  Experiments  of  Motais  would  indicate  that 
the  eye  with  its  immediate  investing  capsule  rotates  in  the  bed  of  fat. 

One  of  the  strong  bands  from  the  aponeurosis  closes  the  sphe- 
noidal  fissure.  It  was  described  by  H.  Mtiller  under  the  name  of 
orbital  muscle,  and  it  is  to  this  band  that  the  term  is  at  present 
more  especially  applied.  It  contains,  like  some  of  the  ailerons,  bun- 
dles of  unstriated  muscular  fibers  which  serve  to  give  it  a  certain 
elasticity  by  which  the  contents  of  the  orbit  are  prevented  from  press- 
ing backward  into  the  sphenoidal  fissure.  It  is  supplied  by  nerve 
fibers  from  the  great  sympathetic,  and  it  is  thought  that  this  fact 
accounts  for  the  sinking  of  the  eye  in  some  cases  of  paralysis  of  cer- 
tain branches  of  that  nerve. 


SECTION  VII. 

THE   VESSELS    SUPPLYING   THE   MUSCLES    OF    THE   EYE. 

AKTEKIES. 

The  ophthalmic  artery,  a  branch  of  the  internal  carotid,  enter- 
ing the  orbit  at  the  orbital  foramen  at  the  external  side  of  the  optic 
nerve  and  rather  below  its  center,  furnishes  the  principal  blood  sup- 
ply to  the  muscles.  Advancing  nearly  horizontally  a  distance  of 
about  three-fourths  of  an  inch,  its  main  trunk  rises  above  the  level 
of  the  nerve  (sometimes  turning  beneath  it)1  and  passes  to  the  inner 
wall  of  the  orbit,  along  which  it  takes  its  course  lying  between  the 
external  rectus  and  the  superior  oblique.  At  the  border  of  the  orbit 
it  divides  into  two  main  branches,  as  the  nasal  and  frontal  arteries. 

As  the  artery  passes  over  from  the  outer  to  the  inner  side  of 
the  optic  nerve,  it  gives  off  several  branches  which  go  to  supply  the 
lachrymal  gland,  the  interior  of  the  eyeball,  the  cellular  tissues  of 
the  orbit,  and  the  six  motor  muscles. 

The  infra-orbital  artery,  branching  from  the  internal  maxillary, 
which  originates  from  the  external  carotid,  in  its  course  through  the 


1  F.  Meyer   ("Morpholog.  Jahrbuch,"  t  xii,  p.  414)   says  that  he  has  ob- 
served this  peculiarity  in  20  cases. 


70 


ANATOMY. 


infra-orbital  canal,  gives  off  branches  which  ascend  to  the  orbit  and 
are  distributed  to  the  internal  rectus,  the  inferior  oblique,  and  the 
lachrymal  gland.  Elschnig  finds  that  in  case  of  obstruction  of  the 
blood  supply  arriving  from  the  internal  carotid,  the  circulation  may 
be  supplemented  from  the  external  carotid  to  the  extent  of  fully  sup- 
plying the  parts  usually  supplied  by  the  internal  carotid. 

VEINS. 

The   ophthalmic    veins,    superior    and    inferior,    are    formed    of 
branches  somewhat  corresponding  to  those  of  the  ophthalmic  artery 


Fig.  20. — Arteries  Supplying  the  Muscles  of  the  Eye.      (Drawing 
by  the  Author.) 

and  which  unite  in  a  single  group  at  the  summit  of  the  orbit  which, 
passing  backward  between  the  heads  of  the  external  rectus,  enters  the 
sphenoidal  fissure  and  opens  into  the  cavernous  sinus.  The  superior 
ophthalmic  is  the  largest  of  the  two  and  corresponds  closely  in  its 
course  with  the  ophthalmic  artery.  It  anastomoses  at  the  internal 
angle  of  the  eye  with  the  frontal  and  nasal  veins. 

The  inferior  ophthalmic  vein  appears  in  the  inferior  part  of 
the  orbit,  receiving  branches  from  the  nose,  the  face,  the  lids,  and 
the  lachrymal  passages,  and  passes  backward  to  unite  with  the  supe- 
rior ophthalmic  vein  or  to  discharge  directly  into  the  cavernous  sinus. 


NERVES  OF  THE  EYE  MUSCLES.  71 

SECTION  VIII. 

THE  NERVES  OF  THE  MUSCLES. 

The  six  motor  eye  muscles  receive  their  innervation  from  three 
cranial  nerves.  These  are  the  third  (oculomotorius  or  oculo-motor) , 
the  fourth  (trochlear),  and  the  sixth  (abducens).  Of  these,  the  third 
nerve  presides  over  the  movements  of  four  of  these  muscles :  the  rectus 
internus,  the  rectus  superior,  the  rectus  inferior,  and  the  inferior 
oblique  muscle.  The  fourth  nerve  acts  upon  the  superior  oblique, 
while  the  sixth  nerve  supplies  the  external  rectus. 


Fig.  21. — Distribution  of  the  Nerves  of  the  Muscles  of  the  Eyes. 
(Drawing  by  the  Author.) 

1.  The  third  (oculomotor)  nerve  (Synon:  N.  oculi  motoris) 
arises  from  a  nucleus  consisting  of  a  column  of  large  yellowish  cells, 
situated  in  the  ventral  floor  of  the  third  ventrical  and  aqueduct  of 
Sylvius.  From  this  group  of  nuclear  cells  the  fibers  in  various  small 
groups  pass  forward  through  the  nucleus  ruber-tegmente  to  the 
pedunculus  corporis  mammillaris,  then,  before  uniting,  emerge  from 
the  brain  substance  at  the  line  of  the  oculomotor  groove  between  the 
two  crura  cerebri,  and  form  a  fasciculus  of  about  a  dozen  cords  which 
unite  at  a  short  distance  from  their  exit  from  the  brain  as  the  third 
cranial  nerve.  The  nerve  at  its  thickest  part  is  about  3  millimeters 
in  diameter  and,  according  to  Krause,  contains  about  15,000  fibers. 
A  small  bundle  of  fibers  passes  through  the  substance  of  the  cms 
cerebri,  then  unites  with  the  main  bundle.  The  origin  of  motor 


72  ANATOMY. 

nerves,  as  a  rule,  is  in  fibers  some  of  which  cross,  and  some  of  which 
are  not  crossed.  In  respect  to  the  oculomotor  nerve  in  man,  the  cross- 
ing of  any  part  of  the  origin  is  questioned  by  some  authors  while 
others  profess  to  have  demonstrated  the  crossing.  According  to  van 
Gudden  (1887),  it  is  shown  that  in  rabbits  the  source  of  this  nerve 
is  of  half-crossed  origin.  In  man,  the  course  of  fibers  from  the  main 
subdivision  of  the  anterior  or  ventral  group  of  cells  of  the  nucleus  is 
characterized  by  a  well-developed  commisural  system  of  fibers  which 
connect  each  nucleus  with  its  fellow  of  the  opposite  side.1  In  the 
diagram  of  Edinger  (Fig.  22)  the  crossing  fibers  are  seen  passing 
from  the  posterior  median  mass  across  the  median  line  to  join  the 
nerve  stem  of  the  opposite  side. 

The  symmetry  of  action  of  the  muscles  of  the  two  sides  which 
are  supplied  by  the  third  nerves  strongly  suggest  their  crossed  origin, 
and  such  a  crossing  is  now  generally  conceded. 

It  has  been  apparently  demonstrated  by  Duval  and  Laborde  that 
the  oculomotor  nerve  of  one  side  is  in  connection,  by  means  of  the 
posterior  longitudinal  bundle,  with  the  abducens  nerve  of  the  oppo- 
site side.2  But  the  observation  of  Xussbaum  on  the  brains  of  kittens 
are  not  in  line  with  this  view.  The  conclusions  of  Bernheimer  will 
be  presented  in  connection  with  the  subject  of  the  nucleus  of  the 
third  nerve. 

The  nerve  makes  its  extra  cerebral  appearance  near  the  internal 
border  of  the  cerebral  peduncle,  immediately  behind  the  pons  Yarolii. 
At  this  point  of  apparent  origin,  it  consists,  not  of  a  single  compact 
nervous  cord,  but  of  from  8  to  12  filaments,  which  at  a  distance  of 
from  3  to  5  millimeters  unite  as  a  single  nerve  and  as  such  proceeds 
toward  the  region  of  its  distribution. 

Passing  forward  and  outward  between  the  posterior  cerebral 
and  the  superior  cerebellar  arteries,  it  emerges  through  the  dura 
mater  at  the  point  where  the  tentorium  cerebelli  unites  with  the  base 
of  the  skull,  and  makes  its  way  along  the  external  walls  of  the 
cavernous  sinus.  It  lies  in  its  course  through  the  cavernous  sinus  at 
the  inner  side  of  the  sixth  nerve  and  of  the  ophthalmic  branch  of  the 
fifth  nerve,  with  which  in  this  region  it  anastomoses.  It  also,  in  this 
part  of  its  course,  anastomoses  with  the  great  sympathetic.  In  its 
course  through  the  cavernous  sinus  it  assumes  a  grayish  aspect,  as  if 


1  Alex.  Bruce:      "Mid  and  Hind  Brain." 

2  Obersteiner:     "Anatomy   of  Central  Nervous    Organs.1'     Translated   by 
Hill,  1890. 


NERVES  OF  THE  EYE  MUSCLES. 


73 


of  a  ganglionic  character.    Penetrating  the  walls  of  the  sinus,  it  enters 
the  orbit  through  the  sphenoidal  fissure  at  its  inner  end. 

Arrived  in  the  orbit,  it  divides  into  two  branches,  the  superior 
and  inferior,  which  are  separated  by  the  nasal  branch  of  the  ophthal- 
mic nerve,  and  which  pass  between  the  two  heads  of  the  external 
rectus. 


Fig.  22. — Diagram  Indicating  the  Origin  of  the  Third  and  Fourth 
Nerves.     (After  Edinger.     By  permission.) 

The  upper  and  smaller  branch  is  continued  forward  above  the 
optic  nerve  to  be  distributed  to  the  superior  rectus  muscle  and  the 
elevator  muscle  of  the  eyelid. 

The  inferior  branch  furnishes  fillets  which  are  distributed  to 
the  rectus  internus,  rectus  inferior,  and  inferior  oblique.  The  branch 
supplying  the  inferior  oblique  sends  a  fillet  to  the  lower  part  of  the 
lenticular  ganglion  and  sends  also  filaments  to  the  rectus  inferior. 

The  branches  of  the  oculomotor  nerve  enter  the  muscles  which 
they  supply  upon  the  surfaces  of  those  muscles  which  are  turned 


74  ANATOMY. 

toward  the  eyeball,  except  in  the  case  of  the  inferior  oblique,  which 
the  nerve  enters  upon  the  outer  side. 

Through  filaments  which  unite  with  the  ophthalmic  branch  a 
connection  is  established  between  the  muscular  root  of  the  third  nerve 
and  the  region  supplied  from  the  ophthalmic  ganglion.  Hence  the 
iris  may  be  involved  in  an  affection  at  the  nuclear  origin  of  this  nerve. 
'This,  however,  as  may  be  seen  from  the  observations  by  Hensen  and 
Volckers  which  will  be  referred  to  later,  and  as  will  appear  when 
the  subject  of  ophthalmoplegia  externa  and  interna  is  discussed,  will 
•depend  upon  the  portion  of  the  nucleus  involved. 

Continuing  behind  the  group  of  cells  constituting  the  nucleus 
of  the  third  nerve  is  another  group  of  large  cells,  with  no  distinctive 
boundary  between  it  and  the  first  group.  This  group  of  cells  (the 
anterior  trochlear  nucleus)  constitutes  the  principal  origin  of  the 
fourth  nerve  (n.  trochlearis),  which  supplies  the  superior  oblique 
muscle.  These  cells  lie  in  a  mass  of  gray  matter  in  the 'plane  of  the 
front  of  the  quadrigeminal  body. 

From  this  rounded  gray  mass  the  main  body  of  fibers  of  the 
nerve  takes  its  origin,  but  farther  back  on  the  dorsal  side  of  the 
posterior  longitudinal  bundle  is  another  group  of  smaller  cells  (poste- 
rior trochlear  nucleus).  Passing  obliquely  backward  and  downward 
ihe  fibers  unite  in  bundles  which  take  a  somewhat  complicated  course 
to  find  their  exit  at  a  point  much  farther  back,  at  the  velum  medullas 
anterius.  In  their  backward  course  the  fibers,  passing  around  the 
walls  of  the  aqueduct  finally,  at  its  roof,  cross  with  their  fellows  of 
the  opposite  side,  the  fibers  of  each  side  finding  their  exit  from  the 
^opposite  side  of  the  roof  of  the  aqueduct  from  their  origin,  at  the 
velum  medullaB  anterius.  While  it  is  certain  that  the  principal  bun- 
dles of  fibers  thus  cross,  certain  lesser  bundles  find  their  exit  from 
the  same  side  with  their  origin. 

From  this  apparent  origin  at  the  velum  medullas  anterius  at  the 
point  of  contact  of  the  two  crura,  and  just  behind  the  corpora  quad- 
rigemina  (valve  of  Vieussens),  the  nerve  proceeds  as  the  smallest  of 
the  cranial  nerves  (its  thickness  being  only  0.4  millimeter)  to  its 
distribution,  the  trochlear  muscle.  The  number  of  its  fibers  is  said 
to  be  about  2150  (Merkel).  Turning  outward,  around  the  superior 
peduncle  of  the  cerebellum,  and  forward  across  the  crus  cerebri,  it 
reaches  the  anterior  portion  of  the  crus  and  proceeds  along  the  trans- 
verse fissure  and  between  the  posterior  cerebral  and  the  superior  cere- 
bral arteries,  and  over  the  internal  carotid  arteries.  Penetrating  the 


NERVES  OF  THE  EYE  MUSCLES. 


75- 


dura  mater  beneath  the  tentorium,  it  continues  its  course  along  the 
outer  wall  of  the  cavernous  sinus,  in  contact  with  and  above  the  oph- 
thalmic nerve  and  outside  the  abducens,  obliquely  crossing  the  third 
nerve,  and  enters  the  orbit  by  way  of  the  inner  end  of  the  sphenoidal 
fissure.  It  is  separated  from  the  other  contents  of  the  cavernous 
sinus  by  a  thin  bony  partition.  As  it  enters  the  orbit  it  passes  above 
the  external  rectus  over  the  levator  palpebrge  and  superior  rectus,  en- 
tering the  upper  surface  of  the  trochlearis  muscle. 

The  nerve  anastomoses  with  a  fillet  from  the  sympathetic  nerve 
in  its  course  through  the  outer  wall  of  the  cavernous  sinus  at  the 


51    TZff 


Fig.  23. — Diagrammatic  Representation  of  Mid-brain  with  Approximate 
Situations  of  the  Nuclear  Groups  from  which  Arise  the  Third,  Fourth, 
Fifth  and  Sixth  Nerves.  (Design  by  the  Author.) 

point  where  it  crosses  the  internal  carotid,  and  also  a  small  branch 
may  unite  this  nerve  with  the  ophthalmic  branch  of  the  fifth  nerve 
through  which,  as  in  case  of  the  third  nerve,  relations  between  the 
nucleus  of  this  nerve  and  the  parts  supplied  by  the  ciliary  nerves  may 
be  established.1  A  small  filament  may  sometimes  be  traced  also  to- 
the  carotid  plexus,  and  one  to  the  infra-trochlear  nerves.2  J.  Stilling 
mentions  also  a  small  root  from  the  cerebellum  which,  passing  for- 
ward without  crossing,  unites  with  the  trochlearis. 

The  Abducens  or  Sixth   Nerve    (synon.   N.   ocularis   externus) 
arises  from  a  nucleus  at  the  floor  of  the  fourth  ventricle  behind  the 


JLuschka:      "Die  Nerven  in  der  Hirnhauten,"  taf.  1,  1850. 
z  Allen:      "System  of  Anatomy,"  p.  518. 


76  ANATOMY. 

nucleus  of  the  motor  root  of  the  fifth  nerve  in  close  connection  with 
the  nucleus  of  the  seventh  nerve.  The  nucleus  consists  of  a  rounded 
mass  of  large  cells.  From  this  nucleus  the  nerve  fibers  pass  toward 
the  medial  line  and  forward  (ventrally)  to  make  their  exit  from  the 
medulla  just  behind  the  pons.  A  small  bundle  of  fibers  from  the 
nucleus  turns  median-wards  and  unites  with  the  fibers  of  the  abclucens 
nerve  of  the  opposite  side.  At  a  point  between  the  anterior  pyramid 
and  the  pons  Yarolii  the  nerve  has  its  apparent  origin.  It  passes 
directly  forward,  pierces  the  dura  mater  to  enter  the  cavernous  sinus, 
in  its  course  through  which  it  lies  close  to  the  floor  in  contact  with 
the  outer  side  of  the  internal  carotid  artery.  It  enters  the  orbit 
through  the  sphenoidal  fissure  below  the  other  nerves  which  enter 
through  the  same  channel,  and  passes  between  the  two  heads  of  the 
external  rectus  to  the  inner  surface  of  which  its  terminal  fibers  are 
distributed.  At  its  entrance  into  the  orbit  it  is  about  2  millimeters 
in  diameter,  and  contains  about  2000  to  2500  fibers.  While  in  transit 
through  the  cavernous  sinus  the  nerve  receives  filaments  from  the 
sympathetic  plexus  about  the  carotid  artery,  and  further  on,  as  it 
enters  the  orbit,  a  branch  from  the  ophthalmic  nerve  also  joins  it. 

Allen  ("System  of  Anatomy")  remarks  that  it  is  found  that 
the  sixth  nerve  is  the  best  example  of  a  motor  nerve  of  all  the  cranial 
series.  According  to  Valentin,  it  is  the  only  member  of  the  ocular 
group  the  section  of  which  fails  to  elicit  evidences  of  pain. 


SECTION  IX. 

NUCLEAR  ORIGIN  OF  THE  NERVES  OF  THE  OCULAR  MUSCLES. 

Situated  in  the  mid-brain  and  in  the  floor  of  the  third  ventricle 
and  extending  from  the  level  of  the  posterior  commissure,  in  front 
of  the  anterior  corpora  quadrigemina  and  backward  to  about  half- 
way between  the  anterior  and  posterior  corpora  quadrigemina  lie 
groups  of  cells  which  give  rise  to  the  three  nerves  supplying  the  oculo- 
motor muscles.  It  is  a  collection  of  several  groups  which  lie  in  some- 
what irregular  order  from  before  backward,  extending  along  the 
floor  of  the  aqueduct  of  Sylvius  to  the  fourth  ventricle,  each  group 
of  which  constitutes  the  nuclear  origin  of  a  cerebral  nerve,  including 
the  third,  fourth,  and  sixth,  which  are  the  nerves  governing  the  mus- 
cles of  the  eyes,  as  well  as  the  fifth  which  also  sends  filaments  to  unite 
with  some  of  the  first  mentioned.  The  figure  above  (Fig.  23)  will 


NUCLEAR  ORIGIN  OF  NERVES. 


77 


serve  as  a  reminder  of  the  general  arrangement  of  the  parts  of  the 
mid-brain  in  which  these  groups  of  cells  are  found,  and  approximately 
the  relative  location  of  this  succession  of  groups. 

The  nuclear  group  of  the  third  nerve  is  the  most  anterior  of 
the  series,  lying  above  (behind)  and  closely  connected  with  the  poste- 
rior longitudinal  bundle  or  fasciculus.  It  is  a  compact  mass,  in 
length,  according  to  Perlia,1  about  10  millimeters,  but  Bernheimer2 


Fig.  24. — Scheme  Showing  the  Different  Groups  of  Nervous  Cells  which 
Constitute  the  Nuclear  Origin  of  the  Common  Oculo-motor  Nerve.  (Dia- 
gram of  Professor  Perlia.) 


gives  the  length  as  6  millimeters.  A  transverse  section  through  the 
masses  shows  two  oval-shaped  bodies,  the  lesser  ends  of  which  ap- 
proach at  the  bottom,  lying  almost  in  contact  with  the  longitudinal 
bundle.  Investigators  have  distinguished  different  collections  of  cells 
in  this  nuclear  group  which  have  been  designated  according  to  the 
results  arrived  at  by  each. 


'"Archiv.  fur  Ophthalmol."  Bd.  35. 
2  "Wurzelgebiet  des  Oculomotorius,"  1894. 
xliv,  Ab.  3. 


"Arch,  fiir  Ophthalmol."  Bd. 


78  ANATOMY. 

Perlia1  distinguishes  the  groups  from  before  backward  as  shown 
in  the  following: — 

1.  Edinger  Westphal  Group. 

2.  Anterior  Lateral. 

3.  Anterior  Dorsal.- 

4.  Central. 

5.  Posterior  Dorsal  and  Posterior  Ventral. 

Dr.  Alexander  Bruce2  gives  the  order  of  the  cell  groups  of  the 
oculomotor  nucleus  thus : — 

A.  An  anterior  group. 

B.  A  postero-external  group. 

C.  A  median  nucleus. 

D.  A  postero-internal  nucleus. 

E.  A  superior  nucleus. 

According  to  Bruce  the  anterior  group  extends  along  the  greater 
part  of  the  oculomotor  nucleus,  lying  closely  upon  the  inner  fibers 
of  the  posterior  longitudinal  fasciculus,  and  may  itself  be  divided 
into  two  subordinate  groups,  of  which  that  lying  nearest  the  nucleus 
for  the  fourth  nerve  is  nearly  circular  and  contains  no  commisural 
fibers  associating  it  with  the  corresponding  subordinate  group  of  the 
opposite  side,  while  the  larger  subordinate  group  has  a  highly  devel- 
oped system  of  commissural  fibers  connecting  it  with  its  fellow  of  the 
opposite  nucleus.3  Even  these  subordinate  groups  are  divided  into 
lesser  collections. 

The  group  B  (postero-external  group),  known  also  as  the  dorsal 
nucleus  of  Erlinger4  and  Siemerling,5  lies  on  the  outer  fibers  of  the 
anterior  fasciculus,  and  is  distinctly  separated  from  the  anterior 
group. 

The  group  C  (median  nucleus)  is  less  extensive  than  the  two 
above  mentioned  and  is  situated  nearer  to  the  median  line.  A  layer 
of  fibers  passes  from  it  to  the  posterior  longitudinal  fasciculus,  some 
of  which  also  join  the  fibers  constituting  the  root  of  the  nerve. 

The  group  D  (postero-internal  nucleus)  is  situated  above  the 
median  nucleus  and  between  it  and  the  posterior  external. 


1  Op.  cit.  Bd.  35. 

2  "Proceedings  of  the  Royal  Society  of  Edinburgh,"  1889-1890. 

3  Bernheimer  states  that  these  crossing  bands  are  not  commissural  but 
are  nerve  fibers.    Loc.  (it.  p.  11. 

4  "Arch,  fiir  Psych.,"  1885,  Zwolf  Vorlesungen. 
6  "Arch,  fiir  Psych.,"  xxii,  Suppl.,  Heft. 


NUCLEAR  ORIGIN  OF  NERVES.  79 

The  superior  nucleus  (group  E)  is  a  small  circular  group  situ- 
ated above  the  posterior  external  group. 

All  of  the  groups  are  connected  by  fibers  with  the  posterior  longi- 
tudinal fasciculus,  and  the  root  fibers  of  the  nerve  pass  forward  in 
separate  bundles. 

Bernheimer,1  as  stated,  gives  the  length  of  the  nuclear  mass  as 
6  millimeters.  He  thinks  that  the  measurement  of  Perlia  is  erroneous 
in  including  the  superior  lateral  nucleus  which  Bernheimer  regards 
as  completely  isolated  from  the  principal  group. 

The  oculomotorious  group,  according  to  him,  borders  directly  on 
the  lesser  trochlcar  group  behind,  left  and  right  from  the  median 
line,  partly  under  the  aqueduct  and  bounded  below  by  the  fibers  of 
the  posterior  longitudinal  fasciculus;  the  two  lateral  portions  of  the 
nucleus  rise  as  though  two  eggs  were  standing  side  and  side  with  the 
small  ends  down  and  approaching  each  other.  The  several  divisions 
which  have  been  described  he  regards  as  illusions  and  considers  the 
nuclear  mass  as  undivided.2  At  the  distal  end  exist  detached  groups 
of  associated  ganglion  cells  which  he  calls  lateral  ganglion  cells,  and 
which  are  in  relation  with  those  of  the  main  group  through  fibers 
which  connect  them. 

Centrally  and  toward  the  anterior  end  there  are  wedge-shaped 
groups  much  as  described  by  others. 

Bernheimer  and  others  believe  that  they  have  established  the 
proof  that  fibers  of  the  optic  nerve  pass  to  the  region  of  the  quad- 
rigeminal  bodies  and  to  the  nuclear  masses  of  the  oculomotor  nerve, 
and  thereby  is  an  association  established .  between  the  sense  of  sight 
and  the  nerves  directing  the  movements  of  the  eyes.3 

According  to  the  experiments  of  Hensen  and  Volckers,4  made 
upon  the  exposed  nucleus  in  dogs  by  electrical  excitation,  the  nucleus 
of  the  oculomotor  nerve  extends  from  the  floor  of  the  third  ventricle 
as  far  forward  as  the  corpora  mamillge  and  backward  along  the  floor 
of  the  aqueduct  of  Sylvius,  until  it  joins  the  nucleus  of  the  fourth 
nerve.  These  observers  concluded  that  they  recognized  separate 
portions  of  this  nuclear  origin  as  presiding  over  the  divisions  of  the 


1  "Wurzelgebiete  des  Oculomotorious  beim  Menschen,"  1894. 

2Loc.  tit.  Page  13. 

*  "Die  Wurzelgebiete  der  Augennerven."  Graefe-Saemisch  Handbuch, 
1900,  Leif,  16,  S.  87. 

4  "Uber  den  Ursprung  der  Accommodations  Nerven,  nebst  Bemerkungen 
iiber  die  Function  der  Wurtzeln  des  Nervus  Oculomotorius;"  Arch,  fiir  Oph- 
thalmol.  Bd.  xxiv,  1,  p.  1,  1878. 


80  ANATOMY. 

third  nerve  distributed  to  different  muscles.  They  locate  these  por- 
tions as  follows :  First,  from  the  floor  of  the  third  ventricle  spring 
the  fibers  governing  the  muscle  of  accommodation  and  of  the  sphinc- 
ter of  the  pupil  and  of  the  tensor  choroideae.  Where  the  aqueduct 
of  Sylvius  enters  the  third  ventricle,  commences  the  source  of  that 
portion  of  the  nerve  governing  the  rectus  internus,  and  behind  this, 
on  the  floor  of  the  aqueduct,  that  governing  the  rectus  superior  and 
the  levator  palpebrae  superioris.  Behind  these  cells  lie,  near  the  cor- 
pora quadrata,  the  origin  cells  of  the  branches  for  the  rectus  inferior 
and  the  inferior  oblique.  In  respect  to  the  origin  cells  of  the  levator 
superioris,  of  the  inferior  rectus,  and  of  the  inferior  oblique,  these 
observers  speak  without  doubt. 

Kahler  and  Pick,1  also  from  the  standpoint  of  pathology,  are  in 
accord  with  Hensen  and  Volckers  that  the  part  of  the  nerve  govern- 
ing the  pupil  has  its  origin  in  the  anterior  portion  of  the  group  of 
nuclear  cells  of  the  nerve,  while  the  innervation  of  the  four  motor 
muscles  arises  from  the  cells  more  posterior,  those  governing  the  up- 
ward movements  of  the  eyes  and  of  the  lids  lying  most  posteriorly. 
In  the  sagittal  direction,  the  extent  of  the  nucleus  in  man  is,  accord- 
ing to  Obersteiner,  5  millimeters,  but  according  to  Perlia,  10  milli- 
meters. Mauthner  gives  these  locations  according  to  Kahler  and  Pick 
in  the  following  scheme : — 

1.  Nucleus  for  the  accommodation. 

2.  Nucleus  for  the  sphincter  of  the  iris. 


I  §   I  8.  Nucleus  for  the  int.  rectus. 


•5    I  4.  Nucleus  for  inf.  rectus. 


5.  Nucleus  for  levator  palp.  sup. 

6.  Nucleus  for  superior  rectus. 

7.  Nucleus  for  inferior  oblique. 


Then  follows: 

The  nucleus  for  trochlearis. 

Bernheimer,2  from  experiments  by  destruction  of  individual  mus- 
cles and  the  resulting  degeneration  of  portions  of  the  nuclear  mass 
in  apes,  arrives  at  the  conclusion  that  the  centers  for  the  origin  of 
the  nerves  are  in  the  following  order  from  behind  forward : — 

1.  Fibers  to  the  internal  muscles   (not  in  the  experiments). 

2.  Eectus  inferior  of  the  eye  of  the  opposite  side. 


1  "Zur  Localization  partieller  Oculomotorius  Lahmungen."     "Prager  Zeit- 
shrift  fur  Heilkunde."  1881. 

*  Archiv  fur  Ophthalmol,  xlvii,  3. 


NUCLEAR  ORIGIN  OF  NERVES. 


81 


3.  Inferior  oblique  of  the  eye  of  the  opposite  side  with  cells  sup- 
plying fibers  to  nerve  for  inferior  oblique  of  the  same  side. 

4.  Rectus  inferior  of  the  same  side  with  perhaps  fibers  to  the 
opposite  side. 

5.  Rectus  superior  of  same  side. 
G.  Levator  palpebrse  of  same  side. 

The  importance  of  these  investigations  justifies  the  introduction 
of  the  results  arrived  at  by  these  various  observers  in  this  place. 

It  has  not  been  ascertained  through  what  course  the  connection 
between  the  nuclear  origin  of  the  nerves  supplying  the  motor  mus- 


Tr. 


Fig.  25. — Professor  Bernheimer's  Diagram  of  the  Nucleus  of  the  Oculo- 
motor and  of  the  Trochlearis  Nerves.  (By  permission  of  Professor 
Bernheimer.) 

cles  of  the  eyes  and  the  cortex  is  established.  In  certain  cases  of 
cortical  disease  the  elevator  muscle  of  the  lid  is  paralyzed,  while  the 
motor  eye  muscles  remain  intact.  This  fact  might  suggest  the  con- 
clusion that  the  fibers  for  the  levator  palpebrae  may  diverge  from  the 
fibers  of  the  other  eye  muscle  nerves  or  that  the  fibers  running  to  the 
very  anterior  portion  of  the  nuclear  mass  are  from  the  affected  part. 
The  angular  gyrus  is  the  supposed  location  of  the  cortical  center 
for  the  levator  palpebrae.  It  would  also  appear  that  the  center  for 
the  coordinate  movements  of  the  eyes  is  located  in  the  superior  frontal 
convolution,  since  a  lesion  at  this  convolution  causes  conjugate  devia- 


82  ANATOMY. 

tion  of  the  eyes  toward  the  side  opposite  the  lesion  and  renders  the 
movements  toward  the  diseased  side  impossible. 

Stimulation  by  electrical  means  of  several  cortical  areas  has 
caused  turning  of  both  eyes  in  the  same  direction  and  toward  the 
side  opposite  to  that  to  which  the  stimulus  is  applied.  These  con- 


Spher* 


Fig.  26.  —  Bernheimer's  Diagram  of  the  Connections  of  the  Nuclei  of  the 
Oculo-motor  Nerve  and  the  Cortex.  (Permission  of  Professor  Bernheimer.) 

jugate  deviations  occur  when  stimulation  is  applied  to  the  occipital 
region  as  well  as  to  the  region  to  which  reference  has  already  been 
made.  The  possibility  of  such  effects  resulting  through  special  con- 
nections between  different  areas  of  the  cortex  renders  the  study  of 
the  subject  through  local  stimulation  difficult  and  inconclusive. 

The  researches  of  Bernheimer  above  referred  to  have,  however, 
more  conclusively  established  the  relation  between  the  angular  gyrus 


NUCLEAR  ORIGIN  OF  NERVES.  83 

and  nerves  governing  the  lateral  and  convergence  movements  of  the 
eyes. 

The  scheme  suggested  by  Bernheimer  of  the  associating  connec- 
tions is  shown  by  the  annexed  diagram,  which  is  copied  by  his  per- 
mission. (Fig.  26.) 

It  will  be  observed  that  the  connection  is  made  through  what  he 
calls  intermediary  or  association  cells  (Schaltzellen). 

Notwithstanding  the  important  researches  of  these  more  recent 
observers  we  are  still  unable,  returning  to  the  nuclear  masses,  to 
make  with  certainty  a  statement  of  the  definite  connections  between 
special  portions  of  the  nucleus  of  the  third  nerve  and  the  special 
muscles  to  which  the  branches  of  this  nerve  are  distributed.  Marina1 
even  raises  the  question  whether  indeed  the  center  for  the  enervation 
of  the  iris  lies  in  the  oculomotor  nucleus. 

Immediately  behind  the  somewhat  extended  collection  of  cells 
forming  the  nucleus  of  the  third  nerve,  and  closely  approximated, 
lies  the  nucleus  of  the  fourth  nerve.  So  closely  are  these  two  masses 
located  that  in  many  instances  it  is  rather  by  the  larger  size  of  the 
cells  of  the  latter  than  by  any  well-defined  special  separation  that  the 
limits  of  the  two  are  to  be  determined.  In  other  cases  there  is  a 
separation  of  a  slight  interval.  The  nucleus  of  the  fourth  nerve  is 
much  less  extended  than  its  neighbor,  is  oval  in  form  and  lies  near 
the  middle  line.  It  is  situated  near  the  depression  which  divides  the 
anterior  and  posterior  corpora  quadrigemina,  and,  like  the  nucleus 
of  the  oculomotor,  lies  above  (dorsally  to)  the  posterior  longitudinal 
bundle  and  below  (ventrally  to)  the  aqueductus  Sylvii. 

The  cylindrical  prolongations  from  which  originate  the  fibers 
of  the  nerve  pass  at  first  outward  and  backward  as  far  as  the  descend- 
ing root  of  the  fifth  nerve,  then  they  curve  around  the  aqueduct  of 
Sylvius,  where,  becoming  more  united,  they  decussate  with  the  bundle 
of  fibers  from  the  opposite  nucleus,  and  forming  the  root  of  the 
nerve,  pass  to  the  side  opposite  to  the  origin  in  the  valve  of  Vieussens 
to  form  the  trunk  of  the  nerve,  whose  course  has  been  described  at 
page  75.  (See  Fig.  23,  N",  IV.) 

If  the  nuclear  masses  of  the  third  and  fourth  nerves  are  in  close 
approximal  relations,  that  of  the  sixth  nerve  is  separated  from  both 
by  a  distinct  and  considerable  interval. 

Between  the  two  former  and  the  latter  is  situated  the  nucleus  of 
the  fifth  nerve,  but  in  a  plane  somewhat  different — more  deeply  in 
the  annular  protuberance.  The  grayish  nucleus  of  the  sixth  nerve 

1  "Uber  Multiple  Augenmuskel  Lahmungen,  1896. 


84  ANATOMY. 

is  situated  in  the  floor  of  the  fourth  ventricle  and  its  position  is 
marked  by  the  eminentia  teres.  It  is  nearly  spherical  in  form  and 
is  surrounded  on  three  sides,  lower,  inner,  and  upper,  by  the  loop 
which  the  fibers  of  the  facial  nerve  make  near  their  origin.  Its  cells 
are  large  and  multipolar. 

At  the  inner  side  it  sends  out  the  fibers  which  unite  to  form  the 
nerve,  which  pass  forward  and  outward  and  finally  leave  the  cerebral 
trunk  at  the  posterior  border  of  the  annular  protuberance. 

Van  Gehuchten1  says  that  a  crossing  of  fibers  from  the  two 
nuclei  of  the  sixth  nerve  has  not  been  found.  Bruce2  describes  a 
special  fasciculus  of  fibers  which  passes  between  the  root  of  the  facial 
nerve  and  the  posterior  longitudinal  fasciculus,  and  crossing  the 
raphe  enters  the  opposite  fasciculus.  In  this  fasciculus  these  fibers 
may  ascend  to  the  third  nucleus.  In  this  case  the  sixth  nerve  would 
supply  fibers  to  the  nerve  supplying  the  internal  rectus  of  the  op- 
posite eye,  while  it  furnishes  the  body  of  fibers  for  the  nerve  directed 
to  the  external  rectus  of  the  same  side  with  itself.  Muscular  action 
from  the  stimulus  of  this  nerve  root  therefore  would  induce  conjugate 
lateral  rotations  of  the  eye  toward  the  side  on  which  the  nucleus  is 
located. 

Fibers  also  pass  to  the  superior  olive,  to  the  external  auditory 
nucleus,  and  to  the  cortex  of  the  opposite  hemisphere. 

Again,  referring  to  Fig.  23,  the  situation  of  this  nuclear  mass 
in  its  relations  to  the  other  nuclear  groups  and  to  the  mid-brain  will 
be  seen. 

SECTION  X. 

CIRCULATION  TO  THE  NUCLEI  OF  THE  NERVES  OF  THE 
OCULAR  MUSCLES. 

The  two  vertebral  arteries  unite  to  form  a  single  trunk,  the 
basilar  artery,  which  lies  upon  the  pons  Varolii.  From  this  trunk 
pass  a  considerable  number  of  branches,  the  course  of  which  is  nearly 
at  right  angles  with  the  main  trunk,  and  which  penetrate  the  pons, 
and  passing  to  the  floor  of  the  fourth  ventricle  and  of  the  aqueduct 
of  Sylvius,  furnish  to  this  region  its  principal  blood  supply. 

These  branches,  unlike  the  vessels  which  supply  the  cortex,  do 
not  divide  in  arborescent  and  anastomosing  branches,  but  pass  directly 


1  "Systeme  Nerveux  de  L'Homme,"  1893,  page  400. 

2  "Mid  and  Hind  Brain,"  p.  12. 


CIRCULATION  TO  THE  NUCLEI. 


85 


as  terminal  vessels  from  the  main  trunk  to  the  region  which  they 
supply.  They  are  almost  parallel  with  each  other,  forming  a  series 
of  direct  and  comparatively  straight  lines.  (Fig.  27.) 

The  trunk  of  the  basilar  artery  also  gives  off  some  larger 
branches,  the  posterior  cerebellar,  the  middle  cerebellar,  and  the 
anterior  cerebellar.  From  these  branches,  also,  small  and  direct 
arterial  twigs  penetrate  the  substance  of  the  pons,  having  the  same 
general  characteristics  as  those  arising  directly  from  the  main  trunk. 


Fig.  27. — Arteries  Supplying  the  Pons  Varolii  and  Mid-brain.  (After 
Duret.) 

A,  Trunk  of  Basilar  artery.  B,  Right  and  left  vertebral  arteries. 
1,  Posterior  cerebellar.  2,  Superior  cerebellar.  3,  Middle  cerebellar. 
4,  Anterior  spinal.  5,  Posterior  spinal. 

The  basilar  artery  and  its  branches  also  send  branches  to  the 
roots  along  the  course  of  the  nerves  arising  from  the  floor  of  the 
aqueduct  and  the  fourth  ventricle.  The  peculiar  arrangement  of  the 
branches  from  these  different  sources  renders  the  parts  supplied  by 
each  isolated  from  each  other,  a  fact  of  no  little  significance  from  a 
pathological  point  of  view. 

A  series  of  veins  resembling  in  their  course  the  arteries  just 
described  empty  themselves  into  a  venous  plexus  which  lies  upon 
the  pons. 


PART  II. 


PHYSIOLOGY. 
SECTION  XI. 

THE  CENTER  OF  MOVEMENTS  OF  THE  OCULAR  GLOBE. 

Before  proceeding  to  the  investigation  of  the  movements  of  the 
eyes,  it  is  important  that  the  position  of  the  center  about  which 
these  movements  are  made  should  be,  as  definitely  as  practicable,  un- 
derstood. 

Much  thought  and  labor  have  been  bestowed  upon  this  subject, 
and  the  results  obtained  by  different  competent  observers  (Miiller, 
Volkmann,  Bonders,  Valentin,  Barrow,  and  others)  have  not  been 
entirely  uniform.  Notwithstanding  some  diversity  in  the  methods 
and  determinations  the  general  results  have  somewhat  approximated. 

Most  of  the  earlier  observers  placed  the  center  of  rotation  very 
nearly  at  the  center  of  the  optic  axis. 

Volkmann,1  as  a  result  of  his  researches  in  regard  to  the  point 
of  crossing  of  the  lines  of  direction  (center  of  similitude),  believed 
that  he  had  also  arrived  at  a  determination  of  the  center  of  rotation, 
that  the  point  of  crossing  of  the  lines  of  direction  and  the  center  of 
rotation  were  identical,  and  that  the  point  was  situated  at  the  middle 
of  the  axis  of  the  eye  (12.50  millimeters  behind  the  apex  of  the 
cornea).  Helmholtz2  and  Barrow,3  while  not  agreeing  with  the 
methods  of  Volkmann  regarding  the  point  of  crossing  of  the  lines  of 
direction,  arrived  at  a  determination  of  the  center  of  rotation  nearly 
accordant  with  that  of  Volkmann,  they  placing  this  center  at  12.40 
millimeters  behind  the  apex  of  the  cornea.  J.  J.  Miiller,  of  Zurich,4 
believed  that  the  center  of  rotation  changes  as  the  eye  is  directed 
upward,  that  the  higher  the  extent  of  upward  rotation  the  further 
is  the  center  removed  from  the  cornea. 


1  "Neue  Beitrage  zur  Physiol.  d.  Gesichtsinns,"  Leipzig,  1836,  Cap.  iv. 

2  "Optique  Physiol.,"  p.  117. 

3  "Beitrage  zur  Physiologic  u.  Physik  d.  Menchl.  Auges."  Berlin,  1841. 

4  Archiv  f.  Ophthalmol.  xiv,  3,  216. 

(86) 


CENTER  OF  MOVEMENTS  OF  THE  OCULAR  GLOBE. 


87 


Bonders,1  recognizing  the  fact  that  ametropia  depends  prin- 
cipally upon  a  difference  in  length  of  the  visual  axis,  concluded  that 
the  distance  at  which  the  center  of  motion  lies  behind  the  cornea 
must  undergo  modifications  depending  upon  the  degree  and  kind 
of  ametropia.  He  therefore  instituted,  in  connection  with  Dover, 
an  investigation  from  which  were  obtained  results  differing  from 
those  previously  accepted. 

According  to  these  results  it  appeared  that  in  the  emmetropic 
eye  the  center  of  motion  i^  situated  at  the  distance  of  1.77  millimeters 
behind  the  middle  of  the  visual  axis. 

Supposing  the  length  of  the  visual  axis  to  be  23.53  millimeters, 
the  average  in  the  emmetropic  eyes  examined  by  him,  the  distance 
of  the  center  of  motion  behind  the  apex  of  the  cornea  averaged  13.5-1 
millimeters,  and  in  front  of  the  posterior  surface  of  the  sclera  9.99 
millimeters. 

In  myopia  the  average  position  was  at  14.52  millimeters  behind 
the  cornea,  and  in  hypermetropia  13.22  millimeters,  while  the  average 
length  of  the  visual  axis  in  the  latter  condition  was  but  22.10  milli- 
meters, thus  placing  the  center  of  motion  2.17  millimeters  behind  the 
middle  of  the  visual  axis. 

The  subjoined  table  gives  the  average  results  obtained  by  Bon- 
ders for  emmetropic,  myopic,  and  hypermetropic  subjects2: — 


a 

Position  of  the  Center  of  Motion 

, 

b 

c 

d 

e 

Length  of 
Visual 
Axis 

Behind 
the 
Cornea 

Before  the 
Posterior 
Surface  of 
Sclerotic 

In  Percentage 
Proportion 

Behind  the 
Middle  of 
the  Visual 
Axis 

Angle  Be- 
tween the 
Axis  of  the 
Cornea  and 
the  Visual 
Line 

mm. 

mm.                 mm.                                                     mm. 

1  E. 
2  M. 
3  H. 

23.5.°) 
25.55 
22.10 

13.54    :       9.99  =  57.32    :    42.46        1.77 
14.52    :      11.03  —  56.83    :    43.17        1.55 
13.22    :       8.88  =  59.8     :    40.2         2.17 

5°  .082 
2° 
7°.  55 

Donders's  method  consisted  in  determining  how  great  the  angles 
of  motion  (with  equal  excursions  on  both  sides)  must  be,  in  order 
to  make  the  two  extremities  of  the  measured  horizontal  diameter  of 


1  "Accommodation  and  Refraction  of  the  Eye." 
2Donders:     Loc.  cit.,  p.  181. 


88  PHYSIOLOGY. 

the  cornea  coincide  alternately  with  the  same  point  in  space.  In  other 
words,  Bonders  proceeded  to  determine  the  center  of  rotation  by 
procuring  the  elements  of  a  triangle,  one  side  of  which,  the  diameter 
of  the  cornea,  was  known,  the  other  sides  being  the  two  lines  pro- 
ceeding from  the  two  extremities  of  this  known  line  to  join  at  the 
center  of  motion. 

To  this  end,  the  diameter  of  the  cornea  was  measured  by  the 
aid  of  the  ophthalmometer  of  Helmholtz,  the  flame  of  a  lamp  being 
placed  perpendicularly  above  the  instrument.  Through  the  oph- 
thalmometer the  image  of  the  flame  was  seen  reflected  on  the  cornea. 
By  means  of  another  lamp,  screened  from  the  ophthalmometer,  the 
cornea  was  illuminated.  The  eye  to  be  investigated  was  given  a 
definite  direction  by  looking  at  a  "sight"  or  mire  which  was  movable. 


Fig.  28.— From  Bonders. 

It  was  easily  possible  to  bring  the  eye  into  such  position  that  the 
reflected  image  of  the  flame  should  appear  exactly  at  the  center  of 
the  cornea.  The  ophthalmometer  giving  double  images,  the  images 
of  the  flame  could  be  made  to  fall  upon  the  extreme  border  of  the 
two  images  of  the  cornea,  as  is  shown  in  the  figure. 

The  number  of  degrees  read  off  on  the  ophthalmometer  required 
to  bring  the  double  image  into  this  position  gave  one-half  of  the 
chord  subtending  the  cornea.  By  turning  the  plates  of  the  instru- 
ment other  confirming  measurements  were  made,  and  the  average 
was  taken  as  representing  the  half  diameter  of  the  cornea. 

This  element  having  been  thus  accurately  determined,  the  next 
step  was  to  ascertain  the  arc  which  the  cornea  must  describe  in  tra- 
versing this  ascertained  distance,  its  own  transverse  diameter. 

A  ring  was  suspended  before  the  examined  eye  in  which  a  fine 
hair  was  perpendicularly  stretched.  It  was  then  ascertained  how 
many  degrees  the  eye  must  be  moved  in  order  that  the  hair  should 
appear  first  at  one,  then  at  the  other  margin  of  the  cornea.  This 
number  of  degrees  corresponded  to  the  angle  which  the  eye  had  de- 


CENTER  OF  MOVEMENTS  OF  THE  OCULAR  GLOBE. 


89 


scribed  from  its  center  of  motion.  This  angle  was  found  to  be  in 
normal  eves  about  50°.  The  knowledge  of  the  diameter  of  the  cornea 
and  of  this  angle  of  motion  then  served  as  data  for  the  determination 
of  the  center  of  motion. 

Giraud-Toulon1  took  exception  to  Donders's  method  on  the 
ground  that  the  arbitrarily  described  arc  chosen  by  Bonders  assumed 
the  very  point  which  was  in  question.  The  method,  he  declared, 
would  be  unassailable  if  this  arc  with  its  arbitrary  radius  could  be 
shown  to  have  its  center  at  the  center  of  movement  of  the  eye.  This 
observer  arrived  at  conclusions  practically  in  accord  with  those  of 
Yolkmann,  Barrow,  and  Valentin,  that  the  center  of  rotation  is  iden- 
tical with  the  center  of  the  globe.  The  methods  of  Giraud-Toulon, 
however,  do  not  appear  to  have  been  sufficiently  exact  to  have  enabled 
him  to  have  arrived  at  technically  correct  conclusions. 

Ludwig  Mauthner2  arrived  at  results  more  in  accord  with  those 
of  Bonders,  yet  somewhat  at  variance  with  them. 

His  average  results  are  shown  by  the  subjoined  table,  as  com- 
pared with  those  of  Bonders : — 

Position  of  the  Center  of  Motion. 


Behind  the  Cornea 

Behind  the  Middle  of  the 
Visual  Axis 

Refraction  ...            .    . 

Bonders 
13.54  mm. 
13.01      " 
14.52      " 

Mauthner 
13.73  mm. 
13.22     " 
15.54     " 

Bonders 
1.77  mm. 

2.17     " 
1.75     " 

Mauthner 
1.24  mm. 

1.47     " 
1.82     " 

Emmetropia              -    .    . 

Hypermetropia  .... 

Myopia  

It  may  be  readily  concluded  that  the  variations  in  the  results 
as  shown  in  the  above  table  might  arise  from  the  selection  of  cases 
for  examination  in  the  groups  for  hypermetropia  and  myopia,  and 
that  the  difference  of  about  0.2  millimeter  in  emmetropia  might  be 
the  result  of  the  difference  in  manipulation,  and  hence  a  difference 
which  may  be  disregarded.  The  center  of  motion  must  necessarily 
be  modified  by  the  size  of  the  globe  of  the  eye.  In  young  children  the 
eye  has  not  reached  its  full  development  and  some  anatomists  have 
stated  that  it  does  not  reach  the  typical  form  of  the  emmetropic  eye 


1889. 


"Contribution  a  la  Physiologic  de  la  Vision,"  Annales  d'Oculist.,  1868. 
2  "Optiche  Fehler,"  pp.   634-649,   1876;    "Augenmuskellamungen,"   p.   475, 


PHYSIOLOGY. 


until  after  a  few  years.  This  view  does  not  seem,  however,  to  be 
sustained  by  recent  investigations.  It  would  seem  that  the  eye  reaches 
its  permanent  form  and  size  earlier  than  other  organs.  The  following 
table  is  made  from  results  of  measurements  of  Weiss,  but  selecting 
only  a  part  of  the  data  given  by  him.  According  to  these  measure- 
ments there  appears  to  be  a  rapid  increase  in  the  size  of  the  eye  during 
the  first  three  or  four  years.  From  that  time  no  very  material  advance 
is  made  before  the  twelfth  year,  but  from  that  forward  to  the  twen- 
tieth there  is  a  steady  growth.  It  is  highly  probable  that  with  a  larger 
number  of  measurements  a  more  uniform  increase  in  the  growth  of 
the  eve  would  be  shown : — 


Subjects 

Sagittal  Diameter 

Horizontal  Diameter 

1  year  and  less     

mm. 

16  to  18  5 

turn. 
15  5  to  19 

21 

21.75 

6  years  old    ....        .    . 

21  3 

21  3 

21 

21.5 

20.5 

20  3 

12  years  old  

21 

20.8 

226 

21.5 

18  years  old  

23.3 

23 

23  8 

24  8 

SECTION  XII. 

DEFINITIONS  OF  TERMS  EMPLOYED  IN  DESCRIBING  THE  POSITIONS 
AND  DIVISIONS  OF  THE  HEAD  AND  OF  THE  RELATIONS  OF  THE 
EYES  AND  OF  OBJECTS  SEEN  TO  THE  HEAD. 

- 

In  determining  the  movements  of  the  eyes  toward  the  objects  to 
which  they  are  directed  it  is  necessary  that  the  position  of  the  head 
be  defined,  that  its  various  mechanical  divisions  be  understood,  and 
that  the  directions  of  the  eyes  in  relation  to  the  position  of  the  head 
be  clearly  stated.  For  these  purposes  a  nomenclature  has  been  adopted 
.by  Henly,1  and  employed  with  some  variations  by  Helmholtz.  The 
definitions  as  given  below  are,  with  some  changes,  condensed  from 
Helmholtz.2 

The  head  is  composed  of  two  symmetrical  parts,  and  the  plane 
which  divides  them  (ab,  Fig.  29)  is  called  the  median  plane.  This 


1  "Handbuch  der  Systematischen  Anatomic." 

2  Optique  physiol.  p.  508. 


DEFINITION  OF  TERMS. 


91 


plane  passes  from  before  backward,  completely  dividing  the  two  parts. 
Sagittal  planes,  or  sections,  are  planes  passing  from  before  backward 
and  parallel  to  the  median  plane  (cd).  Transverse  planes  join  corre- 
sponding parts  of  the  two  sides  of  the  head  (ef);  they  are  perpendic- 
ular to  the  median  plane. 

The  primary  position  is  that  natural  position  in  which  the  head 
is  erect  upon  an  erect  body,  and  the  gaze  is  directed  exactly  in 
advance  (the  lines  of  regard  being  parallel  to  the  median  plane) 
toward  the  horizon.  In  this  position  the  ridge  above  the  root  of  the 


Fig.  29.— Planes  of  the  head. 


nose  will  be,  as  a  rule,  in  a  vertical  line  with  the  teeth  of  the  upper 
jaw.1 

Horizontal  sections,  or  transverse  sections  are  planes  extending 
from  before  backward  when  the  head  is  in  the  primary  position. 

Frontal  sections  are  vertical  sections  perpendicular  to  the  me- 
dian plane. 

Sagittal  lines  are  lines  drawn  from  before  backward  in  the  me- 
dian or  sagittal  planes.  Such  lines  mark  the  intersection  of  the 
sagittal  (or  median)  planes  and  the  horizontal  planes.  The  two  sides 


1  As  there  is  much  irregularity  in  the  position  of  the  teeth,  the  author  has 
chosen  as  fixed  points  the  ridge  above  the  root  of  the  nose,  and  the  point  below 
the  nose,  just  below  the  spine  of  the  superior  maxillary,  the  lips  being  pressed 
so  that  the  distance  from  the  bone  is  equal,  as  nearly  as  possible,  at  the  two 
points.  (See  page  45.) 


92  PHYSIOLOGY. 

of  the  head  separated  by  the  median  plane  are  the  right  and  left; 
and  the  two  sides  as  divided  by  a  sagittal  plane  are  temporal  and 
nasal  or  medial.  The  parts  above  arid  below  a  transverse  plane  or 
section  are  superior  and  inferior,  and  when  for  an  inclined  position 
of  the  head  the  terms  superior  and  inferior  would  not  be  strictly 
applicable,  Serre  proposes  the  terms  frontal  and  jugal. 

The  two  parts  separated  by  a  frontal  plane  are  anterior  and 
posterior. 

The  point  of  regard,  or  the  point  of  fixation,  is  a  point  fixed  by 
the  two  eyes,  the  point  at  which  the  visual  lines  of  the  two  eyes  meet. 

The  line  of  regard  is  a  straight  line  drawn  from  the  object  fixed, 
through  the  center  of  rotation  of  an  eye,  and  to  the  macula. 

The  visual  line  differs  slightly  from  the  line  of  regard,  and  is 
slightly  to  its  external  side,  but  for  the  most  part,  practically,  these 
lines  may  be  regarded  as  identical. 

The  plane  of  regard  is  the  plane  drawn  by  and  included  within 
the  two  lines  of  regard. 

The  base  line  is  the  line  drawn  between  the  centers  of  motion  of 
the  two  eyes,  and  which  therefore  forms  the  base  of  a  triangle  of 
which  the  lines  of  regard  form  the  other  two  sides. 

The  median  line  of  the  plane  of  regard  is  the  line  drawn  from 
the  middle  of  the  base  line  to  the  point  of  fixation,  therefore  bisecting 
the  plane  of  regard. 

The  field  of  regard  is  the  field  which  the  point  of  regard  may 
traverse.  It  is  less  extensive  than  the  visual  field. 

Helmholtz  considers  the  field  of  regard  "as  a  part  of  a  spherical 
surface  of  which  the  center  will  be  at  the  center  of  rotation." 

Every  new  position  of  the  plane  of  regard  with  reference  to  an 
initial  position  may  be  determined  if  the  angle  wrhich  the  newly 
established  plane  forms  with  the  initial  position  is  known. 

The  ascensional  angle  of  regard  is  the  angle  formed  by  the 
primary  and  the  new  position  of  the  plane  of  regard  above  or  below 
the  first.  When  the  plane  is  displaced  toward  the  forehead,  the  sign 
of  the  angle  is  positive;  when  toward  the  chin  the  sign  is  negative. 

Lateral  displacements  of  regard  are  the  displacements  of  the 
lines  of  regard  in  the  plane  of  regard,  and  the  displacements  are 
measured  by  the  lateral  angle  of  displacement.  This  angle  is  posi- 
tive for  displacements  to  the  right,  and  negative  for  displacements 
to  the  left. 


DIRECTION  OF  INFLUENCE  OF  MUSCLES  OF  THE  EYES.          93 

The  ascensional  and  the  lateral  angle  suffice  to  define  the  posi- 
tion of  the  line  of  regard. 

The  globe  of  the  eye  may  execute  movements  about  the  line  of 
regard  taken  as  its  axis,  which  line  may  remain  fixed.  The  extent 
of  such  movements  (wheel-like)  is  called  by  Germans  Raddreliungs- 
winkel,  and  by  writers  in  French  and  English,  torsion.  These  vol- 
untary rotations  are  to  be  discriminated  from  the  leanings  of  the 
vertical  meridians  when  the  eyes  are  in  the  position  of  minimum 
innervation.  These  latter  conditions  are  declinations  and  are  not 
related  to  torsion.  The  extent  of  torsion  is  measured  by  the  angle 
which  a  plane  invariably  joined  to  the  eye  makes  with  the  plane  of 
regard.  For  this  fixed  plane  Helmholtz  selects  the  plane  which  in 
the  retina  coincides  with  the  plane  of  regard  when  that  plane  is  in 
the  primary  position,  and  to  this  plane  he  gives  the  name  of  the 
retinal  horizon.  The  angle  of  torsion  is  the  angle  of  displacement  of 
the  vertical  meridian  when  the  eye  passes  from  the  primary  to  a  sec- 
ondary position.  When  the  superior  extremity  of  the  vertical  me- 
ridian of  the  retina  is  displaced  to  the  right,  Helmholtz  makes  the 
sign  positive;  when  displaced  to  the  left,  negative.  In  this  work 
displacement  to  the  temporal  side  is  positive;  to  the  median  side, 
negative. 


SECTION  XIII. 

DIRECTION  OF  THE  INFLUENCE  OF  THE  VARIOUS  MOTOR  MUSCLES 

OF  THE  EYES. 

All  the  rotations  of  the  eye  occur  about  a  fixed  point  known  as 
the  center  of  rotation.  This  center,  as  we  have  seen,  is  situated  rather 
more  than  a  millimeter  posterior  to  the  center  of  the  optic  axis.  For 
the  practical  purposes  of  the  present  chapter,  in  order  to  reduce  the 
elements  in  the  problems  before  us,  the  center  of  the  optic  axis  may 
be  assumed  to  be  the  center  of  rotation. 

The  six  muscles  which  contribute  to  the  rotations  of  the  eye  are 
divided  into  three  pairs,  and  each  pair  acting  by  itself  alone  causes 
the  eye  to  rotate  upon  a  definite  axis  which  in  every  instance  cuts  the 
center  of  rotation.  In  respect  to  one  pair  (superior  and  inferior 
oblique)  the  expression  "a  definite  axis"  has  to  be  accepted  with  the 
reservation  that  it  is  not  exactly,  but  for  the  purpose  of  this  dis- 
cussion, practically  "a  definite  axis." 


94  PHYSIOLOGY. 

While  it  will  be  necessary  in  this  connection  to  speak  of  the 
action  of  muscles  of  each  eye  to  a  certain  extent  independently,  it  is 
to  be  remembered  that  neither  eye  acts  independently,  but  that,  by 
virtue  of  their  innervation,  the  two  eyes  act  in  definite  relations  and 
associations  with  each  other. 

Hering  has  expressed  this  law  somewhat  as  follows:  "The  two 
eyes  in  their  service  of  the  visual  sense  are  directed  as  though  they 
were  a  single  organ.  To  the  moving  impulse  it  matters  not  that 
this  single  organ  exists  as  two  different  members,  since  it  is  unneces- 
sary that  either  of  the  two  should  be  moved  or  directed  only  for 
itself.  One  and  the  same  impulse  governs  the  two  eyes  at  the  same 
time  as  one  may  with  a  single  rein  guide  a  pair  of  horses." 

While  from  their  peculiar  positions  the  actions  of  the  oblique 
muscles  upon  the  rotation  of  the  globe  are  evidently  not  those  of 
simple  traction  from  side  to  side,  or  directly  up  and  down,  the  in- 
fluence of  the  four  recti  might  at  first  thought  appear  to  be  exercised 
in  the  interest  of  direct  movements,  laterally  or  vertically ;  and  that 
each  pair,  those  acting  laterally  and  those  acting  vertically,  are 
directly  antagonistic  to  each  other. 

That  this  is  not  the  fact  in  the  case  of  the  vertically  acting  recti 
will  presently  appear,  and  the  fact  is  one  of  much  weight  both  in  its 
bearing  upon  the  subject  of  paresis  of  these  muscles  and  upon  tor- 
sions. 

In  regard  to  the  planes  of  action  of  the  rectus  internus  and 
rectus  externus,  they  may  indeed  be  regarded  as  nearly  identical, 
although  as  seen  at  page  55  there  are  variations  from  the  ideal  inser- 
tions and  therefore  variations  from  the  rotations  according  to  the 
rule.  If  a  section  were  made  which  would  cut  the  eyeball  and  the 
two  lateral  recti  in  such  manner  as  that  the  plane  of  the  section 
would  be  identical  with  the  center  of  the  axis  of  action  of  one  of  these 
muscles,  this  plane  should  also  divide  the  other  muscle  in  about  the 
same  manner,  and  the  plane  would  be  carried  through  the  antero- 
posterior  axis  of  the  eyeball.  If  the  attachments  of  these  two  muscles 
were  always  uniform  and  in  the  average  position,  it  might  be  said 
that  the  plane  of  division  in  such  a  case  would  be  identical  in  each 
case.  Unfortunately  for  theories  of  exact  planes  of  the  axis  of  rota- 
tion, this  is  rarely  the  case.1 


^olkmann  ("Berichte  liber  die  Verhandlung  der  Kugel,"  1869)  found  in 
thirty  observations  that  the  action  of  the  internal  and  external  rectus  included 
a  downward  movement  of  the  eye,  with  a  slight  turning  upon  the  antero-pos- 


TRACTION  DIRECTION  OF  MUSCLES. 


95 


Thus  it  results  that  from  a  contraction  of  the  internal  rectus 
alone,  the  eye  with  typical  attachments  of  these  two  muscles  is  ro- 
tated exactly  in  and  undergoes  no  modification  in  its  direction  from 
the  horizontal  plane.  In  like  manner,  by  contraction  of  the  externus 
the  eye  is  rotated  directly  outward,  while  it  still  maintains  its  orig- 
inal relation  to  the  horizontal  plane.  Tlie  axis  of  turning  -for  the  eye 
by  the  influence  of  these  two  muscles  is  therefore  vertical.  Thus,  if 
in  the  diagram  (Fig.  30),  the  line  ab  represents  a  vertical  axis  drawn 


Fig.  30. — Diagram  Indicating  the  Traction  Direction  of  the  Lateral  Recti 
with  the  Axis  of  Rotation  by  these  Muscles. 

through  the  point  of  motion  (center  of  rotation),  by  the  action  of  the 
lateral  recti  the  eye  will  be  turned  exactly  upon  this  axis  and  the  axis 
will  not  be  forced  from  its  original  vertical  position. 

Notwithstanding  the  symmetry  of  action  of  these  two  antagon- 


terior  axis — this  latter  being  less  than  1°.  Since  the  slight  leanings  of  the  axes 
of  rotation  of  the  two  muscles  would  neutralize  each  other,  and  since  a  greater 
number  of  observations  might  result  differently,  this  slight  leaning  may  be 
neglected. 


96  PHYSIOLOGY. 

istic  muscles,  their  course  backward  is  not  correspondent ;  for  whereas 
the  rectus  internus,  after  rounding  the  eyeball,  passes  somewhat 
directly  backward,  and  the  two  interni  approach  each  other  toward 
their  origin  at  an  angle  of  about  10°,  the  course  of  the  externi  toward 
the  point  of  origin  at  the  apex  of  the  orbit  is  much  more  convergent, 
the  angle  of  convergence  being  nearly  65°.  It  follows  that  the  point 
of  action  upon  the  eyeball  is  farther  back  upon  the  eyeball  in  the 
case  of  the  externi  than  in  the  case  of  their  opponents. 

As  in  the  case  of  the  lateral  recti  the  planes  of  the  muscular 
traction  are  nearly  identical,  so  also  is  the  plane  of  the  action  of  the 
superior  and  inferior  recti  practically  common  to  both.  A  plane 
through  the  length  of  one  would  cut  the  length  of  the  other.  Here, 
as  in  the  case  of  the  lateral  recti,  the  absence  of  exactly  uniform 
anatomical  conditions  is  to  be  considered.  Unlike  the  lateral  recti, 
however,  the  course  of  the  superior  and  of  the  inferior  rectus  is  not 
parallel  with  the  antero-posterior  axis  of  the  eye.  From  an  insertion 
upon  the  eyeball,  the  center  of  which  corresponds  nearly  to  a  sagittal 
plane  drawn  through  the  center  of  the  eye,1  but  which  is  obliquely 
placed  with  reference  to  a  horizontal  line  drawn  above  or  below  the 
cornea,  its  inner  extremity  approaches  much  more  nearly  to  this 
line  than  the  outer  extremity,  and  as  is  shown  in  the  diagram  (Fig. 
31),  the  course  of  each  is  backward  toward  its  origin  obliquely  to  the 
axis  of  the  eye  and  inward.  Thus,  if  the  line  of  traction  of  each  of 
these  muscles  now  projected  forward  and  backward,  the  forward  ex- 
tremities of  such  a  projected  line  would  point  toward  the  temporal 
side,  the  other  extremity  inward  toward  the  median  line,  and  if  the 
projection  were  carried  sufficiently  backward  the  lines  of  the  traction 
planes  of  the  two  superior  recti  would  meet  at  a  point  about  an  inch 
behind  the  sella  turcica.  The  lines  projected  backward  from  the  trac- 
tion axis  of  the  inferior  recti  would  also  meet  in  a  like  manner. 
Inasmuch  as  the  center  of  traction  from  the  insertion,  both  for  the 
superior  and  for  the  inferior,  is  nearly  at  the  point  cut  by  a  sagittal 
plane  through  the  center  of  the  eye,  and  as  in  each  case  the  line  of 
traction  is  inward,  it  follows  that  this  line  of  traction  would  fall,  not 
through  the  center  of  rotation,  but  to  the  inner  side  of  it. 

This  will  be  seen  by  the  diagram,  in  which  the  line  ab  is  the 


1  By  a  study  of  the  diagram  Fig.  16,  representing  the  insertions  as  found 
by  Fuchs,  it  will  be  seen  that  in  the  majority  of  cases  the  center  of  the 
insertion  of  the  superior  rectus  is  somewhat  external,  and  that  of  the  inferior 
rectus  somewhat  to  the  nasal  side  of  this  sagittal  plane. 


TRACTION  DIRECTION  OF  MUSCLES. 


97 


optical  axis,  cd  the  horizontal  axis,  d  its  inner  extremity,  e  the  rectus 
superior,  and  e  the  inferior  rectus,  while  the  center  of  rotation  is  at 
the  crossing  of  the  horizontal  and  antero-posterior  axis. 

From  this  arrangement  it  will  be  seen  that  were  all  the  other 
muscles  at  rest  while  both  the  vertically  acting  muscles  were  in  active 
and  equal  contraction,  the  eye  would  be  rotated  upon  the  vertical  axis 
inward. 

The  horizontal  rotation  axis  for  these  two  muscles  is  naturally 
not  at  right  angles  to  the  optic  axis  as  was  the  vertical  axis  in  the 


Fig.  31. — Direction  of  Traction  of  the  Superior  and  Inferior  Rectus  and 
the  Axis  of  Rotation  by  them,  a,  &,  Optic  axis,  c,  d,  Horizontal  axis. 
e  and  c,  Superior  and  inferior  rectus. 

case  of  the  lateral  recti,  but  cuts  it  obliquely,  being  at  a  right  angle 
with  the  course  of  traction  of  the  muscles.  This  rotation  axis  is  in 
relation  to  the  line  of  regard,  according  to  the  determination  of 
Reute1  at  an  angle  of  about  70°.  Mauthner  makes  the  angle  with 
the  transverse  axis  about  30°.  This  axis  of  rotation  then  points  out- 
ward and  backward  and  inward  and  forward  and  in  the  horizontal 
plane  when  the  eye  is  in  the  primary  position. 


1  "Lehrbuch    der    Ophthalmologie,"    1857. 
point  to  be  the  center  of  the  globe. 


Reute   assumes   the  rotation 


98  PHYSIOLOGY. 

But  the  action  of  these  two  muscles  upon  the  eyeball,  as  the 
result  of  their  direction  and  as  a  result  of  the  direction  of  this  ro- 
tating axis,  cannot  be  uniform  under  all  circumstances.  For  whereas 
in  the  primary  position  the  axis  of  rotation  for  these  muscles  is  at 
an  angle  of  about  30°  with  the  transverse  diameter  of  the  eye,  when 
the  eye  leaves  the  primary  position,  through  the  influence,  for  exam- 
ple., of  one  or  the  other  of  the  lateral  muscles,  the  relations  between 
the  axis  of  rotation  and  the  transverse  axis  of  the  eye  must  change. 
In  proportion  as  the  eye  is  moved  outward,  up  to  a  certain  degree, 
the  two  axes  will  be  more  and  more  in  accord,  and  in  proportion  as 
it  is  moved  inward,  up  to  a  certain  degree,  will  the  axes  diverge. 
Thus,  in  rotating  out,  the  angle  at  the  primary  position  formed  by  the 
axis  of  the  eye  and  the  course  of  the  muscles  being  30°,  a  change  of 
the  direction  of  the  optic  axis  outward  30°  would  bring  this  optic  axis 
and  the  axis  of  rotation  coincident,  so  that  in  this  position  the  action 
of  the  two  muscles  together  would  neutralize  each  other  or,  separately, 
one  would  roll  the  ball  directly  up,  the  other  directly  downward  and 
without  rotation  on  the  optic  axis.  On  the  contrary,  could  the  eye 
be  turned  in  60°  from  the  direction  of  the  line  of  regard  in  the 
primary  position  (normally  placed  eyes  cannot  be  thus  turned,  but 
in  some  strabismic  cases  it  is  easily  accomplished),  the  muscles  would 
exercise  their  traction  directly  around  the  antero-posterior  axis,  and 
acting  together  would  rotate  it  inward,  while  acting  separately  they 
would  simply  roll  it  upon  this  axis  without  modifying  its  direction. 

It  will  be  seen  that  at  points  intermediate  to  these  extreme  posi- 
tions the  eye  must  undergo  not  only  a  change  in  the  direction  of  the 
optic  axis  as  the  result  of  the  separate  action  of  the  members  of  this 
pair  of  muscles,  but  it  must  be  caused  to  revolve  upon  the  optic  axis 
as  a  wheel  upon  an  axle,  the  extent  of  this  revolution  depending  upon 
the  angle  made  by  the  transverse  axis  of  the  eyeball  and  the  axis  of 
action  of  the  two  muscles. 

Hence,  if  there  were  to  be  found  upon  the  cornea  a  vertical  white 
line,  this  line,  when  the  eye  would  be  turned  from  the  primary  posi- 
tion inward  (through  the  action  of  the  internus)  and  upward 
(through  the  influence  of  the  superior  rectus)  would  be  observed  not 
only  to  move  inward  and  upward  with  the  general  movement  of  the 
eye,  but  to  tilt  with  its  upper  end  inward,  and  the  farther  the  eye 
were  to  turn  inward  the  more  would  the  originally  vertical  line  lean 
toward  the  median  line  of  the  face. 

On  the  other  hand,  were  the  eye  to  be  turned  outward  more  than 


DIRECTIONS  OF  CORXEAL  MERIDIANS.  99 

30°  and  upward  (action  of  the  extermis  and  superior),  this  white 
line  would  lean  with  the  upper  end  outward  more  and  more  as  the 
eye  would  be  directed  more  and  more  outward. 

Again,  should  the  internal  and  the  inferior  recti  act  together, 
rotating  the  eye  inward  and  downward,  the  vertical  line  upon  the 
cornea  would  lean  with  its  upper  end  toward  the  temple;  but  should 
the  eye  be  drawn  by  the  combined  action  of  the  externus  more  than 
30°  and  by  the  inferior  rectus,  the  line  would  lean  with  its  summit 
nasalward. 

The  diagrams  here  seen  will  illustrate  the  position  of  the  vertical 
corneal  line  under  these  various  circumstances: — 


Fig.   32.— Position   of   Vertical  Meridian   of  the   Cornea   with   Different 
Directions  of  the  Eye. 

A  moment's  consideration  will  show  that  this  revolving  upon 
the  antero-posterior  axis  is  the  result  of  the  peculiar  direction  of  the 
traction  of  the  superior  and  inferior  rectus,  and  not  of  any  complica- 
tion arising  from  the  action  of  the  lateral  muscles,  except  that  by  the 
action  of  these  the  vertically  acting  muscles  are  caused  to  exercise 
their  force  at  different  angles  with  the  optic  axis. 

The  normal  wheel-like  revolutions  to  which  the  eye  is  subjected 
about  the  axis  of  the  eye  under  the  influence  of  contractions  of  the 
muscles,  are  called  by  Helmholtz  and  other  physiologists  torsions ;  and 
to  this  subject  we  shall  return  after  we  have  considered  the  next  pair 
of  muscles,  the  obliques. 

Much  mystery  has  been  thrown  about  the  subject  of  the  action  of 
these  oblique  muscles,  and  some  misleading  assumptions  have  led  to 
errors  respecting  their  actions  and  their  defects,  and  thus  it  has  hap- 
pened that  many  phenomena  arising  from  the  action  of  the  recti  mus- 
cles, if  not  understood  by  the  inquirer,  have  without  hesitation  and 
even  without  inquiry  been  assigned  to  the  action  of  the  oblique  muscles. 
From  what  we  have  already  seen  respecting  the  four  recti  muscles, 
their  action  is  not  so  simpje  as  would  be  the  case  were  all  four  to  act 


100 


PHYSIOLOGY. 


in  line  with  the  line  of  regard.  These  variations  from  the  direct 
and  uniform  action  against  a  fixed  point  have  led  to  a  somewhat 
popular  impression  that  for  all  such  variations  the  oblique  muscles 
must  be  responsible.  The  peculiar  course  and  origin  of  this  pair  of 
muscles  have  encouraged  such  errors.  Listing,  Bonders,  Helmholtz, 
and  others  have  placed  this  subject  clearly  before  us,  yet,  owing  to 
its  apparent  difficulties,  misunderstandings  still  often  arise. 

As  the  two  lateral  muscles  act  through  a  common  plane,  one 


Fig.  33. — Direction  of  Traction  of  the  Superior  and  Inferior  Oblique 
Muscles  with  the  Axis  of  Rotation,  a,  b,  Optic  axis,  c,  d,  Horizontal  axis. 
c,  f,  Axis  of  Rotation  of  Obliques,  o,  Superior  oblique,  o',  Inferior  oblique. 

being  directly  antagonistic  to  the  other,  and  as  also  a  common  plane 
would  cut  the  course  of  action  of  the  rectus  superior  and  inferior, 
so  also  have  the  two  oblique  muscles  approximately  a  common  plane 
of  action,  and,  like  the  other  pairs,  they  are  mutually  nearly  antag- 
onistic. Their  axis  of  rotation  is,  like  that  of  the  superior  and  in- 
ferior rectus,  horizontal  (or  nearl.y  so),  and  this  axis  forms  with  the 
line  of  regard,  according  to  Eeute,  an  angle  of  about  35°  ;  according; 
to  Volkmann  about  39°,  and  according  to  Mauthner  about  40°. 


DIRECTION  OF  ACTION  OF  MUSCLES.  101 

It  is  sometimes  stated  that,  acting  together  against  the  center 
of  rotation,  these  two  muscles  would  rotate  the  eye  inward;  but  that 
singly  the  action  changes.  It  may  be  questioned  whether  the  first 
part  of  the  statement  is  correct ;  this  combined  action,  however,  some- 
times forces  the  eye  forward.  By  the  position  of  its  axis  of  rotation 
each  muscle  singly  swings  the  anterior  pole  of  the  axis  of  the  eye 
outward.  The  contraction  of  the  superior  oblique  (head  and  eye  in 
primary  position)  causes  the  anterior  pole  to  describe  a  curve  down- 
ward and  outward,  while  by  the  contraction  of  the  inferior  oblique 
a  curve  upward  and  outward  is  described.  Neither  the  lateral  nor 
vertical  movement  resulting  from  these  contractions  is  great,  yet  in 
practice  it  is  of  sufficient  account  to  demand  attention.  The  most 
notable  result,  however,  of  the  action  of  this  pair  of  muscles  is  the 
rolling  of  the  eye  upon  its  antero-posterior  axis.  In  this  respect  the 
action  is  similar  to  that  of  the  superior  and  inferior  recti,  but  more 
pronounced.  The  action  of  the  superior  rectus  draws  the  eye  upward 
and  inward,  and  tilts  the  upper  end  of  the  vertical  meridian  of  the 
cornea  inward.  The  superior  oblique,  acting  singly,  turns  the  eye 
downward  and  outward,  and  gives  to  the  vertical  corneal  meridian 
a  turning  of  its  upper  end,  also  inward. 

The  action  of  the  inferior  rectus  depresses  the  eye,  turns  it  toward 
the  medial  line  and  causes  the  vertical  meridian  to  lean  outward. 
The  inferior  oblique  lifts  the  eye,  rotates  it  slightly  outward,  and 
causes  the  upper  end  of  the  vertical  meridian  to  lean  outward. 

As  in  the  case  of  the  rectus  superior  and  inferior,  the  effect  of 
the  action  of  this  pair  also  varies  according  to  the  position  of  the  line 
of  regard  with  respect  to  the  primary  position.  In  proportion  as  the 
line  of  regard  is  carried  to  the  temporal  side,  their  influence  becomes 
less  upon  the  rotation  laterally  and  vertically,  while  the  torsion  be- 
comes greater.  On  the  other  hand,  in  proportion  as  the  line  of  regard 
is  transferred  to  the  medial  side,  the  influence  of  these  muscles  be- 
comes greater  in  vertical  movements  in  proportion  to  the  degree  of 
turning  inward,  while  the  torsion  is  proportionately  reduced. 


102  PHYSIOLOGY. 

KESUME  OF  MOVEMENTS  OF  EACH  EYE  SINGLY. 

Starting  from  the  primary  position,  if  the  movement  were  to  be 
executed  by  a  single  muscle  acting  alone,  always  assuming  a  typical 
insertion  of  the  muscles,  the  resulting  rotations  would  be  such  as  are 
indicated  in  the  following  table: — 


Muscle 


Direction  of  Rotation 


Internal    rectus 
External   rectus 

Superior  rectus 


Inferior  rectus 


Superior  oblique  . 
Inferior  oblique   . 


Directly  to  nasal  side. 
Directly  to  temporal  side. 

{Upward  and  inward  with  rotation  of  the  upper 
end  of  the  vertical  meridian  of  the  cornea  to 
the  nasal  side. 

{Downward  and  inward  with  rotation  of  the  verti- 
cal meridian  of  the  cornea  to  the  temporal 
side. 

(  Downward  and  outward  with  rotation  of  the  ver- 
X         tical  meridian  to  the  nasal  side. 
/  Upward  and  outward  with  rotation  of  the  vertical 
\         meridian  to  temporal  side. 


But  if  we  analyze  the  various  movements  which  can  be  made  by 
an  eye  with  respect  to  the  muscles  required  in  the  execution  of  these 
movements,  we  find  the  results  in  the  following  table: — 

1. — Straight  Movement*. 


Direction 


Muscles 


To  nasal  side    . 
To  temporal  side 
Upward      -    -    . 
Downward     .    . 


Internal  rectus. 

External  rectus. 

Superior  rectus  and  inferior  oblique. 

Inferior  rectus  and  superior  oblique 


2. — Oblique  Movements. 


Direction 


Muscles 


Upward  and  to  nasal  side  .... 
Upward  and  to  temporal  side  .  , 
Downward  and  to  nasal  side  .  . 
Downward  and  to  temporal  side 


( Superior  rectus,   internal  rectus  and  inferior 

\          oblique. 

J  Superior  rectus,  external  rectus  and  inferior 

\         oblique. 

f  Inferior  rectus,  internal  rectus  and  superior 

\          oblique. 

f  Inferior  rectus,  external  rectus  and  superior 

\          oblique. 


ASSOCIATED  MOVEMENTS.  103 

ASSOCIATED  MOVEMENTS  OF  THE  EYES. 

Having  seen  what  are  the  effects  of  the  various  muscles  and  pairs 
upon  the  movements  of  the  eyes  singly,  it  is  necessary  to  inquire  into 
the  relative  movements  by  the  associated  actions  of  the  muscles  of  the 
two  eyes. 

Slight  consideration  will  suggest  that  in  respect  to  single  pairs 
there  may  be  a  loss  of  conformity  of  action  when  the  two  eyes  are 
moved  both  to  the  same  side  of  the  median  plane.  A  critical  study 
will  show  the  reasons  for  this  absence  of  conformity,  and  will  indicate 
the  reasons  for  such  nonconformity  when  corresponding  pairs  only, 
or  when  two  corresponding  pairs  only  act  together. 

Beginning  with  the  internal  and  external  recti  of  the  two  eyes, 
we  find  the  exceptional  instance  in  which  the  associated  movements 
of  the  two  eyes  are,  when  the  ideal  conditions  exist,  in  a  straight  line. 
Thus,  if  the  internus  of  the  right  eye  and  the  externus  of  the  left 
contract  simultaneously,  the  eyes  are  rotated  to  the  left  and  the  plane 
of  regard  will  remain  in  the  same  horizontal  plane.  The  simultaneous 
action  of  the  other  left  internus  and  right  externus  will  induce  cor- 
responding rotation  in  the  same  horizontal  plane  to  the  right.  This 
results  from  the  fact  that  the  plane  of  muscle  traction  of  each  pair  is 
also  the  horizontal  plane  of  the  eye  from  before  backward  and  the 
action  is  around  a  perfectly  vertical  axis.  With  these  side  movements 
arising  from  the  action  of  the  lateral  recti  no  changes  in  the  relative 
position  of  the  meridians  of  the  eyes  are  effected;  thus,  the  vertical 
meridian  of  the  primary  position  remains  vertical  in  the  secondary 
position.  A  study  of  the  actual  insertions  of  this  pair  of  muscles 
shows  that  there  are  many  exceptions  to  this  ideal  adjustment. 

AY  hen  next  we  come  to  the  combined  action  of  the  superior  or 
of  the  inferior  recti  of  the  two  eyes,  the  results  are  different  for  the 
reason  that  the  plane  of  the  muscle  traction  of  each  pair  does  not 
correspond  with  the  vertical  plane  of  the  eye. 

If  the  two  superior  recti  act  together,  they  will  draw  the  two 
eyes  upward,  but  not  in  vertical  or  parallel  lines,  for  the  more  the 
plane  of  regard  is  elevated  the  more  will  the  visual  lines  approach 
each  other.  On  the  other  hand,  if  the  plane  of  regard  is  depressed 
by  the  associated  action  of  the  two  inferior  recti  the  direction  of 
movements  will  not  be  vertically  downward,  but  downward  and  in- 
ward; and  again,  the  more  the  gaze  is  depressed,  the  more  will  the 
visual  lines  approach. 


104  PHYSIOLOGY. 

But  not  only  will  the  movements  of  the  two  eyes  in  raising  and 
depressing  the  plane  of  regard  induce  a  change  from  parallelism  to 
convergence,  the  meridians  will  undergo  a  partial  revolution  (torsion) 
in  such  manner  that  when  the  plane  of  regard  is  raised  by  the  action 
of  these  two  muscles  only  the  upper  extremities  of  the  vertical  me- 
ridian will  roll  toward  each  other,  while  in  depressing  the  gaze  these 
extremities  will  roll  away  from  each  other. 

Passing  to  the  third  and  last  pairs,  the  obliques,  by  the  contrac- 
tion of  the  superior  pair  the  visual  lines  would  be  depressed  and 
caused  to  diverge,  while  the  upper  extremities  of  the  vertical  me- 
ridians would  also  be  wheeled  strongly  toward  each  other.  By  the 
associated  action  of  the  other,  the  inferior  pair,  the  visual  lines  would 
be  raised  and  made  divergent,  and  the  superior  extremities  of  the 
vertical  meridians  would  roll  away  from  each  other. 

Having  traced  the  movements  of  the  eyes  under  the  circum- 
stances of  being  acted  upon  by  single  pairs  of  muscles  acting  in  cor- 
responding directions  upon  each  other,  we  may  next  examine  the  com- 
bined action  of  two  pairs  acting  upon  each  of  the  two  eyes. 

Taking  the  combined  workings  of  the  principal  lateral  rotators, 
the  internal  and  external  recti,  and  the  principal  vertical  rotators, 
the  superior  and  inferior  recti,  the  combined  action  which  will  raise 
the  plane  of  regard  and  at  the  same  time  turn  the  gaze  to  one  side 
will  be  unlike  for  the  two  eyes.  For,  as  the  plane  of  regard  is  raised 
and  the  axis  of  each  eye  is  turned  toward  one  side,  the  lateral  action 
of  the  superior  rectus  of  the  eye  turning  nasalward  is  increased,  and 
its  elevating  action  is  decreased,  the  first  in  proportion  to  the  rota- 
tion inward,  the  last  in  proportion  to  the  angle  of  elevation  of  the 
eye.  On  the  .other  hand,  the  eye  which  turns  temporalward  is  re- 
strained in  its  lateral  movement  by  the  superior  rectus,  while  its  ver- 
tical movement  is  increased  as  it  turns  outward.  Thus  it  follows 
that  were  those  two  pairs  of  muscles  working  in  this  direction  with- 
out the  cooperation  of  a  third  pair,  the  visual  line  of  the  eye  directed 
temporalward  would  be  raised  above  the  visual  line  of  the  eye  turned 
medianward  and  double  vision  at  the  side  would  result,  with  ver- 
tical and  crossed  diplopia.  In  like  manner  diplopia  would  follow  the 
turning  of  the  eyes  downward  and  sideways,  for  the  action  of  the  in- 
ferior rectus  would  increase  the  lateral  movement  of  the  inward  ro- 
tating eye,  while  it  would  impede  that  of  the  outward  turning  one. 
The  depressing  action  of  the  inferior  recti  would  also  be  decreased  for 
the  first  and  increased  for  the  other,  and  as  before  double  vision  would 


ASSOCIATED  MOVEMENTS.  105 

result.  In  each  case  also,  whether  in  depression  or  elevation  of  the 
line  of  regard  with  side  turning,  the  vertical  meridians  of  the  two 
eyes  would  be  subjected  to  tiltings  of  different  extents. 

Combined  for  the  two  eyes  the  action  of  the  recti  superior  or 
inferior  with  either  of  the  oblique  the  results  are  somewhat  dif- 
ferent. Examining  first  the  superior  recti  and  the  superior  obliques, 
the  first  elevators,  the  other  depressors,  the  elevating  power  of  the 
first  would  be  in  some  measure  neutralized  by  the  second,  and  the 
lateral  influence  more  completely;  while  by  a  simultaneous  action 
unregulated  by  other  muscles  the  medial  torsion  of  the  eyes  would  be 
exaggerated.  The  superior  recti  and  inferior  oblique  acting  together 
would  raise  the  eyes,  the  lines  of  elevation  being  parallel,  and  no 
torsion  occurring.  So  also  by  the  combined  action  of  the  superior 
recti  and  the  superior  oblique  will  the  eyes  be  depressed  without  tor- 
sion and  without  convergence. 

From  this  analysis  of  the  workings  of  separate  muscles  and  of 
different  pairs  we  are  prepared  to  examine  the  movements  when  all 
the  muscles  are  considered. 

The  lateral  movements  to  either  side  require,  as  has  already  been 
shown,  only  the  exercise  of  the  force  of  the  lateral  muscles  and  the 
eyes  pass  from  the  primary  to  the  secondary  position  in  the  same  hori- 
zontal plane  without  any  leaning  of  the  vertical  meridians  (torsions). 
In  case  of  irregular  insertions  and  unfavorable  adjustments  of  the 
axes  the  auxiliary  influence  of  other  muscles  may  be  demanded. 

In  all  other  associated  movements  more  than  a  single  pair  is 
called  into  requisition. 

In  the  field  of  regard  (that  field  through  which  the  line  of  regard 
may  be  drawn  by  the  action  of  the  various  muscles)  the  line  of  regard 
may  be  displaced,  not  only  directly  in  the  horizontal  plane  (lateral 
displacement)  and  above  and  below  (ascensional  displacement),  but 
these  lateral  and  ascensional  displacements  may  be  combined  in  all 
directions  within  the  field  of  regard,  passing  from  the  primary  posi- 
tion to  any  other  position. 

These  displacements  have  been  recognized  as  of  five  sorts,  which 
are :  the  lateral,  the  upward,  the  downward,  the  converging,  and  the 
rolling  or  wheel-like  movements.  These  definite  forms,  however,  are 
so  combined  that,  as  stated  in  the  last  paragraph,  the  displacements 
are  in  all  directions. 


106  PHYSIOLOGY. 


SECTION-  XIV. 

SOME   OF   THE   PHENOMENA,   CAUSES   AND   LAWS   OF   TORSIONS 

OF  THE  EYES. 

In  this  section  some  of  the  principles  set  forth  in  the  preceding 
one  will  be  restated  in  order  to  bring  them  directly  in  relation  with 
the  subject  in  hand.  This  is  the  more  excusable  since  there  are  many 
and  serious  difficulties  in  the  way  of  a  complete  mastery  of  the  ab- 
struse problems  presented  by  the  torsions  of  the  eyes  in  their  various 
associated  movements.  Referring  to  one  of  the  accepted  laws  upon 
this  subject,  Mauthner  says:  "Simple  as  is  this  law  and  easy  as  it 
sounds,  it  is  certain  that  no  one  comprehends  it  on  first  hearing  it."1 
The  distinguished  writer  might  have  made  his  declaration  much 
stronger  and  yet  have  been  within  the  limits  of  truth.  Indeed,  so 
confusing  are  the  elements  of  this  subject  that  in  the  enunciation  of 
one  of  its  most  important  laws,  a  law  to  which  he  had  brought  great 
research,  one  of  the  greatest  of  authorities  himself  fell  into  error  in 
its  statement. 

JSTo  apology  is  therefore  necessary  for  such  repetitions  as  may  be 
required  in  order  to  arrange  the  principles  bearing  upon  the  subject 
in  their  order  and  in  direct  connection  with  its  parts. 

About  a  fixed  point,  the  center  of  rotation,  one  pair  of  muscles, 
the  lateral,  rotates  the  eye  on  a  vertical  axis  which  always  remains 
vertical  when  the  rotations  are  induced  by  these  muscles  only  whether 
the  line  of  regard  passes  toward  the  temple  or  toward  the  nasal  side. 
From  the  action  of  these  muscles  alone  therefore  there  is  no  wheel- 
like  rotation  or  torsion  in  any  position  of  the  eye. 

Another  pair,  the  vertically  acting  muscles,  each  rotates  the  eye 
upon  a  horizontal  axis  which  points  to  the  temporal  side  and  back- 
ward and  to  the  nasal  side  and  forward.  From  the  primary  position 
the  action  of  the  superior  rectus  is  to  elevate  the  eye,  turn  it  to  the 
nasal  side,  and  rotate  it  upon  the  optic  axis,  causing  the  horizontal 
meridian  of  the  eye  to  tilt  upward  at  the  temporal  end.  The  action 
of  the  inferior  rectus  from  the  same  position  depresses  the  eye,  turns 
it  to  the  nasal  side,  and  induces  a  rotation  on  the  optic  axis  which 
tilts  the  temporal  end  of  the  horizontal  meridian  of  the  eye  down- 
ward. 


1  "Augenrnuskel  LiUimungen,"  p.  519. 


CAUSES  AND  LAWS  OF  TORSIONS.  107 

The  pair  of  oblique  muscles,  unlike  the  recti  muscles,  which  act 
from  a  fixed  point  behind  the  eye,  have  their  fixed  points  of  traction 
in  front  of  the  equator.  They  rotate  the  eye  upon  an  axis  which  is 
nearly  horizontal  and  points  forward  and  somewhat  to  the  temporal 
side.  The  superior  oblique,  in  the  primary  position,  rotates  the  eye 
somewhat  outward  and  downward,  but  principally  turns  it  on  its 
optic  axis,  causing  the  horizontal  meridian  to  tilt  with  its  temporal 
end  upward.  The  inferior  oblique  rotates  the  eye  outward  and  up- 
ward and  causes  the  horizontal  meridian  to  tilt  with  its  temporal  end 
downward. 

The  line  of  regard  leaving  the  primary  position  in  the  horizontal 
plane  causes  no  change  in  the  action  of  the  lateral  recti,  but  materially 
modifies  the  action  of  all  the  other  muscles. 

The  superior  and  inferior  recti  act  more  and  more  as  simple 
elevator  and  depressor  as  the  eye  is  directed  outward  from  the  primary 
position  to  the  extent  of  30°,  when  they  act  directly  on  a  horizontal 
axis  at  a  right  angle  to  the  course  of  the  muscles.  There  is,  there- 
fore, at  this  point  no  adduction  or  rotation  on  the  optic  axis.  Beyond 
this,  as  the  line  of  regard  is  directed  toward  the  temple,  these  muscles 
increase  the  outward  rotation,  acting  as  abductors,  and  rotate  it  on 
its  optic  axis.  If  the  line  of  regard  is  turned  toward  the  median  line 
the  action  of  these  muscles  becomes  gradually  more  influential  in 
turning  the  eye  toward  the  nose,  and  the  torsion  effect  increases  until 
at  a  supposed  turning  in  of  GO0  their  action  is  only  in  rolling  the  eye 
upon  the  optic  axis. 

The  action  of  the  two  obliques  from  the  primary  position  if  com- 
bined may  force  the  eye  somewhat  forward.  Singly  each  gives  to 
the  eye  an  outward  movement,  the  superior  a  downward,  and  the 
inferior  an  upward  movement,  and  each  rolls  it  on  the  optic  axis. 
This  latter  rotation  is  almost  the  only  result  of  the  action  of  these 
muscles  when  the  line  of  regard  is  directed  medianward  about  35°. 
As  the  line  of  regard  is  directed  outward  the  torsion  from  these  mus- 
cles decreases. 

The  turning  of  the  eye  upon  its  own  antero-posterior  axis  by  the 
direction  of  the  traction  of  the  superior  and  inferior  recti  and  the 
oblique  muscles  as  they  are  above  described,  are  called  torsions.1  All 


1  Helmholtz  says  that  the  rotation  of  the  eye  about  the  visual  line  should 
be  called  Raddrehung,  wheel-movement,  since  the  iris  by  it  rotates  as  a 
wheel.  In  the  French  edition  of  his  great  work  on  "Physiological  Optics"  the 
word  torsion  is  employed,  and  this  among  English  and  French-speaking 
authors  is  the  term  which  has  come  into  universal  use.  That  the  term, 


108  PHYSIOLOGY. 

these  torsions  are  governed  by  fixed  laws  which  would  be  invariable 
were  all  the  factors  in  a  given  movement  of  the  eye  to  remain  uniform. 
In  this  work  torsions  which  tilt  the  upper  end  of  the  vertical  me- 
ridian to  the  nasal  side  (and  elevate  the  external  part  of  the  hori- 
zontal meridian)  are  called  negative.  Those  which  tilt  the  upper  end 
of  the  vertical  meridian  outward  (and  the  outer  part  of  the  hori- 
zontal meridian  down)  are  positive.1 

These  torsions  should  not  be  associated  in  the  mind  with  the  con- 
ditions called  declinations,  to  be  described  in  another  section,  as  they 
are  in  no  way  related. 

We  are  now  in  position  to  discuss  the  movements  of  the  eye  by 
the  combined  action  of  two  or  more  muscles  when  the  eye  is  rotated 
above  or  below  the  primary  plane. 

If  the  line  of  regard  is  carried  directly  upward  the  act  is  not 
effected  by  the  superior  rectus  alone.  This  muscle  may  act  inde- 
pendently, but  in  that  case,  as  shown  above,  the  line  of  regard  would 
be  led  up,  but  also  inward,  and  the  horizontal  meridian  external  to 
the  center  of  rotation  would  tilt  up.  In  other  words  there  would  be, 
with  the  upward  and  inward  movement,  negative  torsion.  The  con- 
sciousness may  take  no  note  of  the  inward  movement  or  of  the  tor- 
sion, but  if  the  movement  is  to  be  directly  upward  and  no  torsion  is 
to  occur,  the  action  of  the  superior  rectus  must  be  supplemented  by 
that  of  the  inferior  oblique.  There  is  no  such  essential  or  automatic 
relation  between  these  two  actions  that  they  must  be  combined,  the 
consciousness  of  the  torsion  determining  the  compensating  action  and 
its  extent.  The  auxiliary  muscle  aids  in  elevating  the  line  of  regard ; 
it  forces  it  outward,  counteracting  the  inward  action  of  the  superior 
rectus,  and  induces  a  positive  torsion  to  compensate  for  the  negative, 
torsion  of  the  superior  rectus. 

It  is  easy  to  see  how,  in  depressing  the  gaze  directly,  the  same 
principles  must  hold,  and  the  two  depressor  muscles,  the  inferior  rec- 
tus and  the  superior  oblique,  must  act  conjointly. 

If  now,  with  an  upward  or  downward  movement,  a  side  move- 


torsion,  is  open  to  objection  cannot  be  denied.  But  since  universal  custom 
has  sanctioned  it  I  have  not  thought  it  wise  to  replace  it  by  any  other. 
Hering  (Lehr.  vom  binokular  Sehen,  1868)  preferred  the  term  Rollung,  which 
does  not  appear  to  be  an  improvement  on  Helmholtz's  term. 

1  Helmholtz  ("Optique  Physiologique,"  p.  601)  calls  all  torsions  to  the 
right  positive  and  to  the  left  negative.  In  this  work,  except  in  the  immediate 
statement  of  Helmholtz's  doctrines,  in  positive  torsions  the  superior  end  of 
the  vertical  meridian  leans  toward  the  temple,  and  in  negative  torsions  toward 
the  median  line. 


CAUSES  AND  LAWS  OF  TORSIONS.  109 

ment  is  introduced,  a  more  complicated  state  arises.  In  such  a  move- 
ment no  less  than  three  muscles  will  be  demanded. 

Let  the  line  of  regard  be  carried  upward  and  to  the  right.  Here 
it  will  be  convenient  to  consider  the  elements  of  movement  of  both 
eyes.  In  this  way  we  will  not  only  arrive  at  the  elements  influencing 
one  eye  when  directed  upward  and  outward  and  of  one  directed  up- 
ward and  inward,  but  also  the  associated  influence  for  blending  the 
images  of  the  two  eyes  may  be  at  the  same  time  observed. 

In  carrying  the  gaze  thus  upward  and  to  the  right,  the  right  eye 
is  thereby  rotated  outward  and  the  left  inward.  Let  it  be  assumed 
that  the  line  of  regard  is  brought  to  its  position  by  the  action  of  the 
external  rectus  and  the  superior  rectus.  Through  the  influence  of  the 
first  a  lateral  movement  only  is  imparted.  Through  that  of  the  sec- 
ond the  eye  is  raised,  but  by  reason  of  the  tendency  of  this  muscle  to 
draw  the  eye  inward  as  well  as  upward,  the  action  of  the  external 
rectus  is  in  some  measure  neutralized.  The  superior  rectus  also  wheels 
the  eye  in  negative  torsion,  forcing  the  vertical  meridian,  to  lean 
inward. 

The  influence  for  inward  rotation  and  that  for  torsion  from  the 
action  of  this  superior  rectus  diminish  in  proportion  to  the  extent  of 
the  outward  rotation. 

Turning  our  attention  now  to  the  left  eye,  we  find  that  the  line 
of  regard  is  directed  inward  by  the  internus  without  any  modification 
of  the  direction  of  the  vertical  meridian,  and  that  this  line  of  regard 
is  also  elevated  by  means  of  the  action  of  the  superior  rectus,  which, 
now  that  the  line  of  regard  is  directed  inward,  also  acts  in  the  lateral 
direction,  assisting  in  the  inward  turning  of  the  eye.  In  proportion 
to  the  extent  of  the  inward  direction  of  the  line  of  regard,  the  in- 
fluence of  the  superior  becomes  more  marked  as  an  adductor,  while 
its  power  fpr  raising  the  line  of  regard  diminishes.  The  elevator 
muscle  also  causes  the  vertical  meridian  to  lean  inward  in  negative 
torsion,  an  effect  which  increases  in  proportion  to  the  rotation  inward. 

If,  now,  it  is  assumed  that  the  influence  in  the  lateral  direction 
of  the  externus  of  the  right  eye  and  of  the  internus  of  the  left  eye  are 
equal,  and  that  the  elevating  influence  of  the  two  superior  recti  are, 
from  the  primary  position,  equal,  there  has  been  induced  a  relation  of 
the  two  eyes  which  must  result  in  confusion  and  diplopia.  For  if  the 
outward  turning  of  the  line  of  regard  of  the  right  eye  is  compared 
with  the  inward  turning  of  the  line  for  the  left  eye,  it  will  be  seen 
that  the  outward  turning  of  the  right  has  been  hindered  by  the  action 


HO  PHYSIOLOGY. 

of  the  superior,  while  the  inward  direction  of  the  line  of  regard  of 
the  left  eye  has  been  assisted  by  the  superior.  The  right  eye  has  been 
elevated  more  than  the  left,  for  the  superior  rectus  has  become  more 
completely  an  elevator  as  the  eye  has  rotated  outward,  while  the  left 
superior  rectus  has  become  less  an  elevator  as  the  eye  has  rotated 
inward.  Hence  the  left  eye  has  outstripped  its  fellow  in  its  lateral 
movement,  but  has  fallen  behind  it  in  the  vertical  movement,  which 
would  induce  homonomous  diplopia,  with  one  image  above  the  other. 
It  is  also  seen  that  each  of  the  vertical  meridians  tilts  in,  the  right 
more  than  the  other,  a  condition  which  would  cause  the  images  seen 
by  the  two  eyes  to  tilt  away  from  each  other  at  the  top.  It  requires 
no  long  consideration  to  perceive  that  such  a  state  of  the  vision  of  the 
two  eyes  would  be  intolerable. 

By  the  action  of  a  third  pair  of  muscles,  the  obliques,  the  rota- 
tions are  so  regulated  and  compensated  that  single  vision  is  made 
possible.  In  many  if  not  in  all  such  complicated  movements  it  is 
probable  that  still  other  muscles  lend  their  aid  in  bringing  about  the 
adjustment.  The  compensating  and  equalizing  actions  above  men- 
tioned are  not  automatic,  performed  as  though  by  interlocked  ma- 
chinery. The  neutralizing  action  of  the  obliques  is  directed  and 
graduated  by  the  will.  It  is  true  that  the  inherited  consciousness  of 
the  relative  actions  of  the  different  muscles  renders  the  will  effort 
easy  and  rapid,  but  it  is  no  less  an  independent  action. 

After  this  analysis  of  the  muscular  actions  involved  in  looking 
up  and  out,  it  will  be  easy  to  form  a  similar  analysis  of  the  elements 
of  a  downward  and  outward  direction  of  the  gaze.  It  is  unnecessary 
to  enter  upon  the  details,  since  the  principles  and  facts  already  shown 
can  be  readily  applied. 

Having  considered  the  primary  and  compensating  forces  which 
influence  the  line  of  regard  in  parallel  directions,  let  us  next  con- 
sider the  elements  that  enter  into  convergence  with  depression  of  the 
lines  of  regard.  The  position  of  the  eyes  in  reading  is  an  important 
one  and  at  some  times  is  a  long-continued  position. 

In  this  position  of  the  lines  of  regard  they  may  be  supposed  to 
be  directed,  each,  downward  and  inward.  Under  these  circumstances 
the  inferior  recti  not  only  act  the  part  of  depressors  and  of  auxiliaries 
to  the  internal  recti  as  convergers,  they  also  tilt  the  superior  part 
of  the  vertical  diameter  of  the  eye  outward,  inducing  positive  torsion, 
and  the  greater  the  convergence  with  a  given  degree  of  depression, 


CAUSES  AND  LAWS  OF  TORSIONS.  HI 

and  the  greater  the  depression  with  a  given  extent  of  convergence,  the 
more  considerable  is  the  torsion. 

When  we  come  to  discuss  the  Law  of  Listing  we  shall  find  that 
in  the  interest  of  clear  vision  a  certain  amount  of  tilting  out  of  the 
meridians  is  necessary  when  the  gaze  is  thus  directed.  But  as  a  result 
of  the  action  of  the  two  muscles  already  mentioned,  this  tilting  may 
be  in  excess  or  insufficient.  In  either  case  a  compensating  action  is 
demanded  of  the  superior  obliques,  and  this  is  an  entirely  independent 
action  governed  by  the  will.  Should  the  obliques  be  thus  called  on, 
they  also  act  to  restrain  the  converging  action  of  the  interni,  while 
they  supplement  the  depressing  action  of  the  inferior  recti. 

As  a  matter  of  fact  these  three  pairs  act  together  so  nearly  auto- 
matically that  the  agency  of  the  obliques  in  restraining  the  conver- 
gence, in  supplementing  the  depression,  and  in  modifying  the  tilting, 
are  all  very  nearly  proportioned  to  the  demands  of  the  situation. 

If  the  lines  of  regard  Avere  to  be  converged  and  depressed  while 
each  line  should  be  directed  through  the  tube  of  an  instrument  ar- 
ranged on  the  principle  of  the  clinoscope,  there  would,  under  these 
circumstances,  be  found  marked  positive  torsion  for  each  eye.1 

Thus  far  we  have  mainly  considered  the  torsions  induced  by  in- 
dividual muscles  acting  in  the  planes  of  their  traction,  with  the  com- 
pensating action  of  supplemental  muscles  when  the  eye  is  directed  in 
various  ways.  We  have  now  to  consider  another  class  of  more  or  less 
oblique  positions  of  the  horizontal  meridians  which  have  been  known 
as  torsions,  but  which  differ  essentially  from  those  which  have  been 
already  described.  They  are  due  to  the  combined  action  of  two  or 
more  muscles  of  the  eye  when  the  gaze  is  directed  in  different  parts 
of  the  field  of  regard. 

Torsions  of  the  former  class  depend  upon  the  direction  of  the 
insertion  of  the  tendon  upon  the  eyeball  and  the  absence  of  accord- 
ance between  the  plane  of  traction  of  the  individual  muscle  and  the 
line  of  the  optic  axis.  In  the  so-called  torsions  about  to  be  discussed, 
there  is  no  rotation  of  the  cornea  about  the  optic  axis,  although  the 
horizontal  meridian  of  the  cornea  rotates  from  the  true  horizon. 

If  we  are  to  use  the  same  term  to  describe  the  two  classes  of  phe- 
nomena, we  should  at  least  limit  the  term  in  the  present  class  by  call- 
ing them  torsions  of  orientation.  In  the  first  class  the  torsion  is  in- 


1  A  normal  negative  declination  might  to  some  extent  neutralize  the  tor- 
sion, but,  as  above  remarked,  all  anomalies  are  supposed  to  be  eliminated  from 
the  present  discussion. 


1 12  PHYSIOLOGY. 

duced  by  a  force  acting  on  the  globe  obliquely  to  the  optic  axis  and 
rotating  the  eye  around  that  axis.  In  the  case  of  the  torsions  of 
orientation,  or  what  might  be  better  termed  plagiotropia,1  the  pole  of 
the  globe  is  urged  by  forces  acting  nearly  at  right  angles  to  each  other, 
and  the  yielding  of  the  pole  to  these  forces  is  in  the  same  manner  in 
which  the  pole  of  any  globe  would  respond  to  similarly  acting  forces. 
The  line  of  regard,  yielding  to  the  action  of  the  two  forces  combined, 
is  directed  to  its  new  position  as  it  would  be  were  a  single  force  applied 
in  a  direction  between  these  two  and  parallel  with  the  optic  axis,  at  an 
angle  depending  upon  the  comparative  influence  of  the  two  actual 
forces.  In  a  movement  induced  by  a  supposed  muscle  thus  placed,  the 
eye  would  change  direction  more  or  less  obliquely  in  connection  with, 
but  not  around,  the  optic  axis.  If  this  principle  could  be  well  under- 
stood it  would  relieve  the  subject  of  the  tiltings  of  the  meridians  in- 
duced by  oblique  movements  of  the  eyes  of  many  of  the  technical  diffi- 
culties which  have  been  associated  with  the  subject. 

Listing  expressed  the  change  of  direction  of  the  axis  of  rotation 
in  the  well-known  and  much  discussed  proposition  known  as  Listing's 
Law.  It  is  as  follows2 : — 

"When  the  line  of  regard  passes  from  the  primary  position  to 
any  other  position,  the  angle  of  the  torsion  of  the  eye  is  the  same  as 
though  the  eye  had  come  to  this  position  by  turning  upon  a  fixed  axis, 
perpendicular  to  the  first  and  second  position  of  the  line  of  regard." 

In  this  law  no  account  is  taken  of  the  real  torsions  which  may 
be  induced  by  individual  muscles  and  we,  following  this  precedent, 
may  formulate  the  law  in  three  sections  thus: — 

I.  When  the  line  of  regard  passes  from  the  primary  position  to 
any  oblique  position  the  meridian  which  corresponds  to  the  plane 
of  movement  of  the  line  of  regard  remains  unchanged  in  its  relation 
to  the  horizon,  while  every  other  meridian  changes  this  relation. 

II.  The  horizontal  meridian  occupies  the  plane  to  which  it  would 
come  if  the  eye  had  rotated  upon  an  axis  passing  through  the  equator 
and  the  center  of  rotation  of  the  globe  and  at  right  angles  to  the  line 
of  regard  in  its  second  position. 

III.  When  the  signs3  of  the  lateral  and  ascensional  angles  are  the 


1  77X07405,  slanting;  rpoTros,  a  turn. 

2  Listing's  Law  appeared   first  in   Rente's  Lehrbuch   der   Ophthalrnologie, 
1853. 

8  In  this  work  the  turning  of  the  line  of  regard  to  the  temporal  side  or 
upward  is  regarded  as  positive,  while  the  turning  of  the  line  of  regard  of  either 
eye  to  the  medial  side  or  downward  is  negative.  The  tilting  of  the  vertical 


CAUSES  AND  LAWS  OF  TORSIONS.  113 

same  for  either  eye,  the  leaning  of  the  horizontal  plane  is  negative. 
When  the  signs  of  the  ascensional  and  lateral  angles  are  unlike  for 
the  two  e}"es,  the  leaning  of  the  horizontal  plane  is  positive. 

These  slopings  or  tilting?,  these  plagiotropic  movements  of  the 
meridians  resulting  from  orientation,  are  not  then,  it  may  be  repeated, 
true  torsions.  The  term  torsion  has  been  employed  here,  but  the  term 
in  this  connection  should  be  regarded  as  plagiotropia  only.  It  is  to 
be  remembered  that  they  are  meridional  tiltings  plainly  separated 
from  the  torsions  arising  from  the  oblique  actions  of  different  indi- 
vidual muscles. 

Bearing  in  mind  the  influence  which  a  single  muscle  acting 
parallel  to  the  optic  axis  and  placed  at  any  angle  in  which  an  oblique 
movement  of  the  eye  is  to  be  made,  it  will  not  be  difficult  to  under- 
stand in  what  direction  the  vertical  meridian  would  tilt  with  any  given 
oblique  movement. 

Bonders  sums  up  the  principle  in  the  words :  "To  a  determined 
position  of  the  line  of  regard  there  responds  a  determined  and  in- 
variable value  of  the  angle  of  torsion"  (meridional  tilting  or  plagio- 
tropia). 

Helmholtz  has  formulated  the  principle  of  meridional  tiltings 
in  a  law  which  is  easy  to  remember.  He  applies  the  sign  "positive" 
to  the  angle  up  and  to  that  to  the  right.  "Xegative"  he  applies  to  the 
angle  down  or  to  the  left.  The  sign  for  the  tilting  is  positive  to  the 
right,  negative  to  the  left.  Bearing  this  meaning  of  the  terms  in 
mind,  the  law  is  plain,  and  its  correctness  or  incorrectness  can  be  easily 
verified  by  placing  a  rubber  ball  with  the  vertical  meridian  marked 
in  ink  in  a  fixed  ring  and  moving  the  ball  in  the  different  directions. 
Careful  experiments  will  show  that  the  law  is  not  correctly  stated. 

The  law  as  stated  by  Helmholtz  is  as  follows: — 

"When  the  ascensional  and  lateral  angles  are  both  of  the  same 
sign  the  torsion  is  negative,  if  they  are  of  contrary  signs  the  torsion  is 
positive/'1 

The  real  facts  resulting  from  this  principle  are,  stating  them  in 
the  terms  positive  and  negative  as  used  by  Helmholtz  and  not  as  used 
in  this  work: — 

1.  Eight  eye,  line  of  regard  directed  upward  and  to  the  right 
(ascensional  angle  4-,  lateral  angle  +),  torsion  to  the  right  -)-• 


meridian  toward  the  temple  is  positive,  toward  the  medial  plane  negative. 
Hence  the  tilting  of  the  temporal  part  of  the  horizontal  plane  down  is  posi- 
tive. 

1  "Optique  Physiologique,"  p.  603. 


114 


PHYSIOLOGY. 


2.  Left  eye,  line  of  regard  directed  upward  and  to  the  right 
(ascensional  angle  -(-,  lateral  angle  -(-),  torsion  to  the  right  -)-. 

3.  Eight  eye,  line  of  regard  directed  downward  and  to  the  right 
(ascensional  angle  — ,  lateral  angle  +  ),  torsion  to  the  left  — . 

4.  Left  eye,  line  of  regard  directed  downward  and  to  the  right 
(ascensional  angle  — ,  lateral  angle  -f)>  torsion  to  the  left  — . 

Comparing  now  these  facts  with  the  law  as  announced  by  Helm- 
holtz,  we  find  that  there  is  a  radical  difference ;  for  while  the  law  de- 
clares that  with  like  signs  the  sign  of  torsion  is  negative,  the  facts 
show  that  with  like  signs  the  torsion  is  positive,  and  with  unlike  signs 
the  torsion  is  negative. 


Fig.  34 


Fig.  35 


Stevens's  Ophthalmotrope. 


The  disagreement  between  the  facts  and  the  rule  might  be  ac- 
counted for  on  the  theory  of  a  misprint  did  not  the  context  forbid 
this  view.  Others  have  discovered  this  error,1  but  the  explanations  to 
prove  the  error  have  been  sometimes  worse  than  the  original  error. 
It  is  reasonable  to  suppose  that  one  so  familiar  with  the  philosophy  of 
torsion  as  the  great  physiologist  might  very  easily  substitute  for  the 
objective  phenomena  of  torsion  the  subjective  phenomena,  as  shown 
by  accidental  images,  of  which  we  are  presently  to  speak.  This,  it 

1  Le  Conte,  Mauthner  and  other*. 


ACCIDENTAL  IMAGES.  115 

appears  to  me,  is  the  explanation  of  the  inconsistency  of  the  law  with 
the  objective  phenomena.  It  would  be  an  error  extremely  easy  to 
make  without  implying  any  false  view  on  the  part  of  the  master. 

We  may  therefore  write  Helmholtz's  law  thus:  When  the  ascen- 
sional and  the  lateral  angles  are  both  of  the  same  sign,  the  torsion  is 
positive;  if  they  are  of  contrary  signs  the  torsion  is  negative. 

For  illustrating  the  positions  of  the  meridians  in  the  different 
adjustments  of  the  eyes  I  have  devised  the  model  or  ophthalmotrope, 
on  the  principle  of  that  of  Reute,  shown  in  Figs.  34  and  35.  A  glance 
at  Fig.  34  shows  the  eye  in  the  primary  position  with  the  horizontal 
meridian  exactly  horizontal  and  the  vertical  meridian  precisely  ver- 
tical. As  the  eye  rotates  up  and  to  one  side  (Fig.  35)  it  is  seen  that 
the  curve  of  the  horizontal  meridian  strikes  the  border  of  the  cornea 
at  the  right  about  2  millimeters  above  the  point  at  which  it  cuts  the 
border  at  the  left.  Also,  the  point  at  which  the  vertical  meridian  cuts 
the  border  of  the  cornea  above  is  about  2  millimeters  to  the  left  of 
the  point  where  it  meets  the  border  below. 

Thus  it  will  be  seen  that,  if  we  regard  the  model  as  representing 
the  left  eye,  a  turning  up  (-)-)  and  to  the  right  (-{-),  the  torsion 
(plagiotropia)  is  to  the  right  (  +  ).  Or,  if  we  regard  the  model  as 
representing  the  right  eye,  we  have  unlike  signs  with  plagiotropia  to 
the  left  ( — ).  Thus  the  law  as  announced  by  Helmholtz  should  be 
restated,  as  I  have  shown  above. 

ACCIDENTAL  IMAGES. 

Having  thus  traced  the  workings  of  the  various  muscles  in  turning 
the  eye  upon  its  center  of  rotation  while  the  lines  of  regard  of  the  two 
eyes  arc  parallel,  and  having  observed  the  objective  effects  of  these 
workings  upon  the  relative  positions  of  the  eyes,  we  may  next  turn  our 
attention  to  some  subjective  phenomena  which  illustrate  and  confirm 
the  facts  already  stated. 

For  this  purpose  we  may  avail  ourselves  of  the  study  of  accidental 
images — a  method  of  investigation  introduced  by  Eeute.1  Such  images 
are  the  result  of  the  principle  that  after  a  strong  impression  has  for 
a  considerable  time  been  presented  to  the  same  portion  of  the  retina, 
that  part  of  the  retina  becomes  dulled  in  its  sensibility  to  that  par- 
ticular impression. 

For  example,  if  one  looks  at  a  white  spot  on  a  dark  background 


1  "Das  Ophthalmotrop."      Gottingen,  1845. 


116 


PHYSIOLOGY. 


for  some  time,  and  then  turns  the  eyes  away  to  look  at  some  neutral 
surface,  there  will  appear  a  dark  spot  on  the  surface,  which  represents 
the  point  in  the  retina  which  has  become  dulled  to  the  extent  that  it 
no  longer  sees  the  neutral  surface  uniform,  but  in  the  absence  of  a 
strong  stimulant  at  that  point  gives  the  impression  of  a  point  not 
well  illuminated.  In  the  same  manner  the  retina  becomes  dulled  to 
the  sensibility  of  a  particular  color  which  may  be  presented  continu- 
ously to  it,  but  in  turning  the  eye  away  from  it  the  complementary 
color  may  appear  in  its  place. 

In  the  experiments  with  accidental  images  this  last  class  of  phe- 


Fig. 


Fig.  37 

Positions  of  Accidental  Images.    From  a  Horizontal  Line. 

nomena  is  especially  available,  and  for  the  methodical  system  of  re- 
search by  its  means  we  are  indebted  to  Bonders.1 

Upon  the  wall  of  a  neutral  tint,  preferably  of  a  light  gray,  the 
observer  fastens  a  strip  of  red  ribbon  horizontally  and  at  a  level  with 
his  eyes.  Sitting  at  a  distance  of  several  feet  from  the  wall,  and 
maintaining  the  primary  position,  he  directs  the  eyes  fixedly  at  the 
ribbon  and  at  its  center,  which  may  be  marked.  After  half  a  minute 
or  more  the  observer  will  see  a  light  halo  all  about  the  ribbon,  and 
he  may  now  remove  his  gaze  to  any  selected  point  upon  the  wall.  As 


1  "Hollandische  Beitrtige,"  Bd.  i,  1848,  S.,  105. 


ACCIDENTAL  IMAGES. 


117 


soon  as  the  gaze  is  fixed  he  will  observe  an  image  in  light  green  of 
the  form  and  size  of  the  red  ribbon. 

If  in  the  experiment  the  gaze  has  been  directed  exactly  above  the 
band,  the  greenish  band  will  appear  above  the  red  one  and  exactly 
parallel  to  it  (b.  Fig.  36),  so  if  the  gaze  is  carried  downward  the 
accidental  image  will  appear  parallel  with  the  original  (c.  Fig.  36). 
If  the  gaze  is  transferred  to  a  point  in  the  same  horizontal  plane  with 
the  ribbon,  but  laterally,  toward  the  right  or  left,  the  secondary  image 
will  be  in  the  same  horizontal  line  with  the  other  (d.  Fig.  36). 


.D 


Fig.  38. — Diagram  from  Helmholtz.  These  curved  lines  represent  the 
inclination  of  the  horizontal  and  vertical  images  when  projected  upon  a 
plain  wall.  If  a  is  the  point  first  fixed,  the  accidental  image,  as  the 
regard  passes  from  a  to  some  other  point,  the  position  of  the  accidental 
image  will  conform  to  the  direction  of  the  line  on  which  the  regard 
rests. 

If,  however,  the  gaze  is  directed  to  any  other  position,  the  acci- 
dental image  will  no  longer  form  a  continuation  of  the  line  of  the 
original  band  nor  remain  parallel  with  it.  If  the  regard  is  carried 


118 


PHYSIOLOGY. 


above  and  to  one  side,  or  below  and  to  one  side,  the  accidental  image 
will  tilt,  and  this  tilting  will  correspond  invariably  with  the  direction 
of  the  gaze,  so  that  from  the  tilting  of  the  accidental  image  the  posi- 
tion of  the  eyes  could  be  deduced. 

Helmholtz  suggests  a  method  for  exact  and  somewhat  elaborate 
observations  of  these  images,  to  which  we  need  here  only  refer.  The 
results  of  such  observations  have  been  so  carefully  recorded  that  tables 
indicating  the  value  of  the  angles  of  torsions  have  been  prepared.  We 
may,  without  entering  into  this  minute  detail,  quickly  verify  the 
general  results. 

If  we  look  first  at  the  horizontal  ribbon  and  then  direct  the  line 
of  regard  upwards  and  to  the  right  we  shall  see  the  accidental  image 
with  its  right  end  higher  than  the  left.  Or,  applying  the  terms 
applied  to  the  meridian  of  the  eye,  the  image  tilts  to  the  left,  as  at 
c.  Fig.  37;  but  if  the  gaze  is  directed  upward  and  to  the  left  the 


\ 


Fig.  39. — Position  of  Accidental  Images  from  a  Vertical  Line. 

accidental  image  will  appear  with  its  left  end  higher  than  the  right 
(b.  Fig.  37),  that  is,  the  image  now  tilts  to  the  right.  So  if  the  gaze 
is  directed  downward  and  to  the  right,  the  accidental  image  tilts  down 
at  the  right  extremity,  as  at  e;  and  when  the  gaze  is  directed  down 
and  to  the  left,  the  tilting  is  as  shown  at  d. 

There  is  a  series  of  effects  apparently  contrary  to  those  just  men- 
tioned if  the  ribbon  is  placed  vertically.  For  now,  if  the  regard  is 
carried  from  the  ribbon  to  the  right  and  upwards,  the  upper  extremity 
of  the  accidental  image  will  lean  to  the  right  (a.  Fig.  39),  while  if 
the  gaze  is  directed  to  the  right  and  downward  the  image  tilts  to  the 
left  (b.  Fig.  39).  If  the  gaze  is  carried  upward  and  to  the  left  the 
image  tilts  to  the  left ;  if  downward  and  to  the  left  the  tilting  is  to  the 
right.  These  apparently  contradictory  results  are  forcibly  illustrated 
when  a  cross  composed  of  a  horizontal  and  vertical  ribbon  is  substi- 
tuted for  the  single  ribbon,  for  now  if  the  line  of  regard  is  carried 
from  the  cross  upward  and  to  the  right  the  horizontal  limb  of  the 


ACCIDENTAL  IMAGES.  119 

cross  will  lean  to  the  left,  while  the  vertical  part  will  lean  to  the  right 
(c.  Fig.  39). 

These  facts  are  not,  as  they  at  first  appear,  in  contradiction  of 
the  first  series  of  observations,  hut,  as  Helmholtz  has  indicated,  the 
apparent  incongruity  depends  upon  the  fact  that  the  plane  of  the  wall 
does  not  coincide  with  the  plane  of  regard  or  with  a  line  at  right 
angles  to  it. 

Professor  LeConte1  placed  an  experimental  plane  in  such  a  way 
that  the  line  of  sight  is  at  right  angles  to  this  plane  when  the  gaze  is 
turned  up  and  out,  down  and  out,  etc.,  and  thus  obtained  results  uni- 
form with  the  laws  of  torsion  in  all  positions.  To  obtain  correct 
results  it  is  necessary  either  that  the  accidental  image  be  projected 
upon  a  surface  which  will  in  every  case  be  at  right  angles  to  the  line 
of  regard,  that  is,  upon  the  inner  surface  of  a  sphere  at  the  center  of 
which  the  eyes  are  in  position,  or  that  the  plane  (wall)  upon  which 
the  observations  are  made  shall  be  marked  with  lines  which  shall  rep- 
resent a  series  of  spherical  coordinates,  in  which  case  these  lines  may 
in  the  calculations  replace  the  direct  horizontal  and  vertical  lines. 
The  diagram  (Fig.  38)  from  Helmholtz  shows  the  inclinations  for 
the  horizontal  and  vertical  images  for  different  positions  of  the  line 
of  regard  when  the  secondary  image  is  projected  upon  a  plane,  vertical 
surface,  as,  for  example,  the  wall  of  a  room.2 

The  law  of  accidental  images  projected  upon  a  spherical  surface 
then  may  be  formulated  thus : — 

When  the  line  of  regard  is  elevated  and  directed  to  the  right  the 
accidental  image  tilts  to  the  left.  When  directed  to  the  left,  the  image 
tilts  to  the  right. 

When  the  line  of  regard  is  depressed  and  directed  to  the  right, 
the  accidental  image  tilts  to  the  right ;  when  directed  to  the  left,  the 
image  tilts  to  the  left. 

Hence,  using  the  terms  positive  and  negative  as  they  are  employed 
in  this  work — positive  indicating  the  temporal,  negative  the  medial 
side — and  again  positive  indicating  above  and  negative  below,  the  law 
of  accidental  images  may  be  stated  thus : — 

When  the  ascensional  and  lateral  signs  are  alike  for  either  eye, 
the  sign  of  the  accidental  image  for  that  eye  is  negative ;  when  the 


JLe  Conte:      "Sipht,"  p.  173. 

2  Dr.  Karl  Grossman,  Liverpool,  usin»  a  transparent  perimeter  band, 
concludes  that  no  rotation  occurs  about  the  optic  axis.  This  is  the  conclu- 
sion which  I  have  above  expressed  at  page  111. 


120  PHYSIOLOGY. 

ascensional  and  lateral  signs  differ  for  either  eye.,  the  sign  of  the  acci- 
dental image  for  that  eye  is  positive. 

Thus  it  will  be  seen  that  there  exists  an  actual  conformity  be- 
tween the  objective  torsions  of  the  eye  on  its  optic  axis  and  the  direc- 
tions of  the  secondary  images  when  projected  upon  a  surface  the  parts 
of  which  are  at  right  angles  to  the  line  of  regard,  for,  since  the  lines 
of  sight  cross  at  the  nodal  point,  the  tilting  of  the  accidental  image 
to  the  left  indicates  an  actual  tilting  of  the  cornea  to  the  right.  This 
important  principle  seems  to  have  been  lost  sight  of  in  the  discussions 
of  the  subject. 

We  have  in  the  discussion  continued  to  use  the  Avord  torsion.,  not- 
withstanding the  fact  that  there  is  no  torsion,  in  deference  to  the  man- 
ner in  which  the  subject  has  heretofore  been  treated.  It  would,  as 
already  remarked,  be  much  in  the  interest  of  clear  thinking  and  cor- 
rect understanding  of  this  somewhat  difficult  subject  were  the  mis- 
leading term  torsion  absolutely  abandoned  for  this  special  class  of 
phenomena  and  if  some  other  term  or  phrase  were  to  be  substituted.1 

While  the  law  for  the  inclining  of  the  corneal  meridians  holds  for 
distant  vision  when  the  visual  lines  for  the  two  eyes  are  practically 
parallel,  there  must  be  some  modifications  of  the  phenomena  when  the 
visual  lines  are  converged. 

The  examination  of  these  phenomena  is  somewhat  more  difficult 
than  those  just  considered  for  an  observer  who  has  not  been  carefully 
and  patiently  trained  in  this  class  of  observation.  When,  as  it  hap- 
pens in  experiments  in  this  field  of  research,  the  retinal  impressions 
are  such  as  to  contradict  our  ordinary  experiences,  both  the  mental 
and  physical  powers  are  brought  to  bear  to  annul  the  supposed  false 
impression.  Thus  it  may  happen  that  accidental  images  formed  for 
the  two  eyes  which  do  not  normally  coincide  within  several  degrees 
may  appear  to  an  observer  to  be  absolutely  coincident  because  the 
divergence  is  mentally  suppressed. 

The  inclinations  of  the  corneal  meridians,  the  actual  torsions  or 
plagiotropic  inclinations  in  convergence  will,  of  course,  vary  accord- 
ing to  the  ascensional  angle  and  the  distance  of  the  point  of  conver- 
gence. 

If  we  take  as  the  first  position  of  convergence  one  in  which  there 
is  no  ascensional  angle,  that  is,  one  in  which  convergence  is  made  in 
the  primary  plane,  there  will,  in  perfectly  adjusted  eyes,  be  no  in- 


1  See  page  112,  where  the  term  pldffiotropia  is  suggested. 


LEANING  OF  CORNEAL  MERIDIANS.  121 

clination  of  the  corneal  meridian,1  that  is,  no  torsion  of  either  eye. 
In  this  plane  convergence  for  any  distance  demands  only  the  action 
of  the  laterally  acting  muscles  and  no  inclination  of  the  meridian 
results  from  their  action.  But  if  the  plane  of  regard  is  depressed  the 
adjustments  for  both  eyes  will  be  relatively  symetrical,  that  for  the 
left  eye  being  the  same  as  when  in  parallel  vision  the  line  of  regard 
is  downward  and  to  the  right.  Eeferring  to  our  law  it  will  be  seen 
that  in  that  case  the  angle  of  ascension  for  the  left  eye  was  negative, 
as  was  (according  to  our  use  of  the  terms)  the  lateral  angle.  This 
would  result  in  a  positive  torsion  for  that  eye.  In  convergence  with 
depression  of  the  line  of  regard  the  torsion  would  be  uniform  and  posi- 
tive for  both  eyes. 

For  the  purpose  of  this  examination  the  newer  model  of  the  clino- 
scope,  with  shorter  tubes  than  the  original  model,  which  may  be  con- 
verged at  fifteen  inches  from  the  eyes,  is  serviceable.  The  tubes  can 
be  depressed  at  any  angle  below  the  horizon,  and  the  objective  may 
remain  vertical.  By  means  of  this  instrument  it  is  easy  to  show  that 
in  convergence  with  depression  of  the  line  of  regard  there  is  a  positive 
or  outward  leaning  of  the  vertical  meridian  of  each  cornea,  and  that 
the  leaning  corresponds  with  the  demands  of  Listing's  Law.  On  the 
other  hand  it  appears  that  when  the  plane  of  regard  is  elevated  above 
the  primary  plane  with  convergence,  the  vertical  meridians  lean  toward 
the  median  plane. 

By  mathematical  calculation  the  extent  of  the  leaning  of  the 
vertical  meridians  may  be  determined.  On  the  next  page  is  found  a 
table  from  Helmholtz2  indicating  the  value  of  the  torsion  at  different 
degrees  of  the  ascensional  and  lateral  angles.  The  table  indicates  the 
torsion  for  a  single  eye. 

It  is  to  be  remarked  that  in  experiments  upon  the  leaning  of  the 
vertical  meridians  in  convergence  the  ordinary  stereoscope  is  of  little 
practical  use  except  it  be  in  showing  to  what  proximal  extent  correc- 
tions through  voluntary  torsional  action  may  be  made  in  the  interest 
of  binocular  vision.  Nor  is  the  effort  which  expert  persons  are  able 


1  This  statement  is  not  in  accord  with  that   of  Helmholtz,  that  in  the 
primary  position  the  eyes  roll  out  1°  15'  each.      Nor  of  Le  Conte  ("Sight,"  p. 
203),  that  the  "two  eyes  in  convergence  roll  out,"  to  show  which  he  introduces 
diagrams  and  experiments.      Only  in  cases  of  some  anomaly  of  adjustment  do 
these  rollings  out  occur  in  the  primary  position.      These  observers  have  mis- 
taken their  own  peculiarities  of  adjustment  for  the  typical  adjustment  of  the 
eyes. 

2  "Optique  Physiologique,"  p.  607. 


122 


PHYSIOLOGY. 


Table  Indicating  the  Extent  of  Torsions. 


Lateral 
Angle 

ASCENSIONAL    ANGLE 

5°              10°            15° 

20° 

25° 

30°              35° 

4O° 

5° 

0°  13' 

0°  26' 

0°  40' 

0°  53' 

1°  7' 

1°  20' 

1°  35' 

1°  49' 

10° 

0°  26' 

0°  53' 

1°  19' 

1°  46' 

2°  13' 

2=  4.f 

3°  1C 

3°  39' 

15° 

0°  40' 

1°  19' 

1°  59' 

2°  40' 

3°  21' 

4°  2' 

4°  45' 

5°  29' 

2J° 

0°  53' 

1°  46' 

2°  40' 

3°  3i' 

40  29' 

5°  25' 

6°  22' 

7°  21' 

25° 

1°  7' 

2°  13' 

3°  21' 

4°  29' 

5°  38' 

6°  48' 

8°  0' 

9°  14' 

30° 

1°  21' 

i°  41' 

4°  2' 

5°  25' 

6°  48' 

8°  13' 

9°  39' 

11°  8' 

35° 

1°  35' 

3°  10' 

4°  45' 

6°  22' 

t.°  0' 

9°  39' 

11°  21' 

13°  6' 

40° 

1°  49' 

3°  39' 

5°  29' 

7°  21' 

9°  14' 

11°  8' 

i:;°  6' 

15°  5' 

to  make  to  unite  stereoscopic  images  without  the  aid  of  the  stereoscope 
more  satisfactory. 

Notwithstanding  the  above  remark  the  stereoscopic  diagrams  on 
the  opposite  page  may  aid  in  illustrating  the  directions  of  the  vertical 
meridians  of  the  eyes  when  the  lines  of  regard  are  converged  and 
depressed  below  the  horizon. 

If  the  page  of  the  book  is  held  up  so  that  the  diagrams  are  at 
right  angles  to  the  line  of  regard  in  the  primary  position  the  lines 
running  horizontal!}1"  and  those  running  vertically  unite  perfectly  and 
remain  in  union  without  effort  indefinitely.  But  if  the  book  is  laid 
flat  upon  the  table  while  the  head  maintains  nearly  the  primary  posi- 
tion, the  lines  do  not  perfectly  coalesce.  When  they  appear  to  do  so 
the  image  leans,  but  the  lines  waver  in  and  out,  standing  not  parallel, 
but  the  vertical  ones  leaning,  those  of  the  right  diagram  to  the  left, 
those  of  the  left  diagram  to  the  right;  while  the  horizontal  lines 
cross  at  the  center,  those  of  the  right  diagram  rising  above  the  others 
at  the  right,  those  of  the  left  diagram  rising  at  the  left.  In  a  diagram 
such  as  this,  in  which  the  impulse  to  fusion  is  feeble,  the  presence  of 
an  anomalous  declination  of  even  a  very  low  degree  may  induce  the 
leaning.  Hence  the  diagram  is  much  less  satisfactory  than  the  use 
of  the  clinoscope  in  which,  the  lines  being  properly  adjusted  for  the 
normal  declination,  the  torsional  phenomenon  is  shown  when  depres- 
sion and  convergence  occurs. 

If,  with  body  erect,  the  head  is  caused  to  lean  toward  one  shoulder 
there  will  occur  a  rotation  of  the  eyes  on  the  visual  line,  but  when 


LEANING  OF  CORNEAL  MERIDIANS.  123 

this  leaning  of  the  head  is  carried  to  a  considerable  extent  the  eye 
rotations  do  not  follow  in  proportion.  This  can  be  shown  by  experi- 
ments with  accidental  images. 

In  the  exposition  of  the  various  laws  which  govern  the  relative 
movements  of  the  eyes  as  they  are  directed  for  fixation  in  different 
parts  of  the  field  of  regard  they  have  been  stated  from  the  mechanical 
and  technical  point  of  view.  It  is  to  be  recalled  that  in  the  living 
subject  great  latitude  is  to  be  conceded  to  the  psychologic  element  in 


Fig.  40. — Illustration  of  Correspondence  of  the  Images. 

the  act  of  vision.  Movements  which  should  be  executed  according  to 
the  laws  which  have  been  stated  are  often  neglected,  and  other  move- 
ments which  are  inconsistent  with  these  laws,  are  often  executed.  In 
the  first  contingency  the  consciousness  of  the  propriety  of  a  given 
movement  may  take  the  place  of  the  movement  itself;  in  the  second 
a  similar  consciousness  of  the  movement  demanded  permits  of  a  varia- 
tion of  the  movement,  the  judgment  making  due  allowance  for  the 
departure  from  the  rule. 


124  PHYSIOLOGY. 

SECTION  XV. 
VISUAL  PERCEPTION  OF  SPACE. 

Visual  perceptions  of  space,  that  is,  of  distance,  of  form,  and 
of  depth,  arise  from  movement  impulses  rather  than  from  the  tradi- 
tional "picture  on  the  retina."  The  retina  indeed  receives  from  the 
object  seen  sensations  of  color,  of  light  and  shade,  but  the  idea  of 
space  and  of  the  position  and  form  of  objects  in  space  is  derived  from 
the  muscular  impulse  which  is  demanded  in  moving  the  eye  in  such 
directions  as  to  bring  these  color  points  successively  upon  a  single 
part  of  the  retina,  or  from  the  consciousness  of  the  expenditure  of 
force  which  might  be  required  to  execute  this  movement.  There  are, 
indeed,  circumstances  under  which  the  mind  arrives  at  an  estimation 
of  the  movement  which  would  be  required  even  when  this  movement 
is  not  executed.  The  intensity  and  the  extent  of  a  muscular  act  may 
be  estimated  before  the  movement  is  executed,  and  hence  in  case  of 
instantaneous  impressions  in  which  time  fails  for  the  actual  perform- 
ance of  muscular  action,  the  mental  consciousness  of  the  extent  of  the 
impulse  which  the  movement  would  demand  is  accepted  for  the  move- 
ment itself.1 

The  point  in  the  retina  from  which  all  judgments  of  direction  or 
distance  are  calculated  is  that  of  clearest  vision,  the  center  of  the 
macula.  If  a  given  point  of  an  object  in  space  is  selected  by  the  mind 
for  fixation  by  the  eye,  there  is  at  once  set  in  motion  a  process  by 
which  the  macula  is  brought  into  line  with  this  selected  point. 

Wundt2  characterizes  this  process  as  reflex.  But  instantaneous 
though  it  is,  and,  so  far  as  we  can  determine,  possibly  without  the 
various  stages  of  logical  purpose,  it  would  seem  to  be  extending  the 
meaning  of  the  term  reflex  beyond  its  legitimate  definition  to  accept 
it  in  this  connection.  That  it  is  a  subliminal  phenomenon  is  certain, 
but  of  its  reflex  nature  there  is  a  reasonable  doubt.  That  the  muscles 
of  the  eye  respond  with  a  rapidity  and  an  accuracy  which  is  amazing, 
to  the  purpose  of  bringing  the  image  of  a  selected  point  from  a  pe- 
ripheral part  of  the  retina  to  the  macula,  and  that  we  cannot  trace 
the  stages  of  mental  activity  from  the  desire  to  see  the  point  to  the 


1  Thus,  in  the  experiment  of  Dove,  stereoscopic  images  appear  united  when 
illuminated  by  an  electric  spark,  giving  too  little  time  for  any  actual  adjust- 
ment of  the  eyes  for  such  union  to  occur. 

2  "Human  and  Animal  Psychol.,"  p.  128. 


VISUAL  PERCEPTION  OF  SPACE.  125 

adjustment  of  the  eyes  for  the  reception  of  its  image  at  the  macula 
is  marvelous!)'  true.  This,  however,  does  not  necessarily  place  the 
phenomenon  within  the  category  of  reflex  actions,  if  by  such  we  are 
to  understand  a  nervous  impulse  which  passes  by  a  short  cut,  failing 
to  reach  the  seat  of  general  consciousness  there  to  give  origin  to  a  pur- 
pose, which  purpose  is  executed  under  the  direction  of  the  will. 

If  one  sees  an  iron  pound  weight  and  takes  it  in  the  hand,  there 
is  before  the  act  a  very  close  judgment  of  the  muscular  impulse  re- 
quired to  lift  it.  So  closely  is  the  judgment  formed  that  should  the 
supposed  iron  weight  prove  to  be  an  imitation  made  of  pasteboard, 
the  hand  would  fly  upward  when  the  weight  was  taken  and  there  would 
result  a  rather  unpleasant  muscular  disappointment.  A  like  disap- 
pointment would  follow  if  the  real  iron  weight  should  be  held  down 
by  a  concealed  magnet.  It  can  hardly  be  thought  that  the  appearance 
of  the  iron  weight  determines  a  reflex  movement  of  the  muscles  of 
the  arm,  there  must  be  a  mental  conception,  based  upon  experience, 
of  the  extent  and  character  of  the  nervous  impulse  and  muscular  con- 
traction required  for  lifting  the  weight. 

Of  a  like  nature,  but  of  infinitely  greater  delicacy  of  judgment  and 
rapidity  of  action,  may  we  suppose  the  movement  of  the  eye  to  be  for 
adjusting  the  image  upon  the  macula. 

One  of  the  most  important  acts  in  respect  to  the  judgment  of  form, 
size,  and  distance  of  objects,  and  the  fact  which  is  perhaps  least  promi- 
nent in  the  minds  of  those  whose  attention  has  not  been  especially 
called  to  it,  is  that  these  judgments  are  largely  based  upon  what  is 
known  as  the  muscular  sense.  This  sense  may  reside  in  the  muscles 
themselves  or  in  the  nervous  centers  from  which  the  nerves  supplying 
the  muscles  originate,  or,  indeed,  in  the  nerves  supplying  the  parts 
which  are  in  contact  with  the  muscles. 

Helmholtz  says  that  we  are  to  distinguish  under  the  term  mus- 
cular consciousness  a  number  of  sensations  essentially  different. 

Thus  we  may  perceive : — 

1.  The  intensity  of  the  effort  of  the  will  by  which  we  endeavor 
to  cause  the  muscles  to  act. 

2.  The  tension  of  the  muscles,  that  is,  the  force  with  which  these 
muscles  strive  to  act. 

3.  The  result  of  the  effort  which,  independently  of  its  percepti- 
bility by  the  other  senses,  notably  by  those  of  sight  and  touch,  are 
indicated  externally  by  an  effective  shortening  of  the  muscle  which 


126  PHYSIOLOGY. 

may  manifest  itself  also  by  a  change  of  tension  in  the  skin  which 
covers  it.1 

To  this  list  of  sensations  as  given  by  Helmholtz  I  have  elsewhere 
suggested  that  there  should  be  added  another  element  which  cannot  be 
classed  as  a  sensation.  This  is  the  consciousness  of  the  intensity  of 
the  will  effort  required  to  accomplish  the  muscular  change,  and  which 
may  be  formed  before  the  will  impulse  has  been  transmitted  to  the 
muscles.2  In  other  words,  an  element  of  the  muscular  sense  is  the 
knowledge  gained  by  experience  of  the  individual,  or  inherited  from 
the  experience  of  others,  of  the  intensity  of  the  will  impulse  demanded 
for  the  execution  of  a  muscular  act. 

It  will  be  seen  when  we  come  to  study  the  phenomena  of  stra- 
bismus (see  page  3G9)  that  an  eye,  the  movements  of  which,  by  reason 
of  unfavorable  adjustments  of  the  organ,  have  been  mentally  disre- 
garded, becomes  (or  remains)  practically  a  blind  eye  because  of  the 
absence  of  experience  of  any  definite  relation  between  the  movements 
of  the  eye  and  the  idea  of  space.  If  circumstances  demand  that  ex- 
perimental knowledge  of  this  relation  should  be  established,  and  a 
definite  understanding  is  arrived  at  by  which  the  mind  recognizes  the 
value  of  the  eye  movements,  and  the  eye  learns  to  act  definitely  under 
the  guidance  of  the  will,  the  sense  of  sight  perceptions,  even  of  the 
most  favorable  character,  may  be  developed. 

This  muscular  act,  as  has  been  stated,  owing  to  the  exceeding 
brevity  of  the  time  during  which  it  may  be  required,  may  not  in  fact 
be  executed,  yet  the  mind  may  accept  the  judgment  of  the  required 
impulse  in  place  of  the  actual  sensation  of  movement. 

Ideas,  then,  of  spatial  relations  of  objects  in  the  field  of  view 
depend  on  the  muscular  sense  experienced  in  bringing  different  points 
which  lie  in  the  field  of  view  to  coincide  with  the  central  point  of  the 
fovea.  If  the  image  of  one  given  point  in  the  field  of  vision  lies  more 
at  the  periphery  of  the  retina  than  another,  the  first  point  will  re- 
quire a  greater  change  in  the  position  of  the  eye,  that  is,  more  exten- 
sive muscular  effort  to  bring  the  image  to  the  macula  than  the  second 
whose  image  is  not  so  far  removed  from  the  macula,  and  hence  the 
first  will  be  seen  as  further  from  the  original  point  of  regard  than 
the  other. 

Xot  only  the  extent  of  movement,  but  the  direction  of  that  move- 


1  "Optique  Physiologique,''  p.  762. 

"Stevens:      "The  Horopter."      Psychological  Review,  April,  1904,  etc. 


VISUAL  PERCEPTION  OF  SPACE.  127 

ment,  enters  into  the  conception  of  the  spatial  relation  between  two 
points. 

The  eye  does  not  start  from  an  indifferent  point  to  wander  aim- 
lessly over  the  surface  of  an  object  to  be  viewed,  but  starting  from  a 
selected  point  it  passes,  in  directing  the  line  of  regard,  from  one  se- 
lected point  to  another,  until  the  form  of  the  object  has  been  mentally 
determined.  It  does  not  follow  that  the  line  of  direct  sight  must 
compass  in  every  detail  the  outline  or  sweep  over  the  surface  of  the 
object.  We  have  already  seen  that  much  is  left  to  the  processes  of 
unconscious  conclusions.  These  combined  movements  of  the  eyes  in 
directing  the  lines  of  regard  as  they  sweep  over  the  surface  of  an  object 
or  a  landscape,  or  the  mental  estimate  of  the  movements  required, 
constitute  the  basis  for  the  conception  of  the  form  and  size  of  the 
object  or  the  outlines  of  the  landscape. 

A  considerable  number  of  elaborate  experimental  researches  has  recently 
been  undertaken,  in  Germany,  in  America  and  elsewhere,  principally  in  psy- 
chological laboratories,  with  the  view  of  establishing  definite  facts  relating  to 
the  fixation  of  points  in  the  field  of  vision  and  to  the  movements  of  the  eyes 
in  the  interest  of  the  space  percept.  Photographic  aid  has  been  brought  to  the 
service  of  these  investigations.  Interesting  as  are  most  of  these  experiments, 
the  deductions  from  them  are  not  conclusive,  and  in  all  there  is  the  notable 
absence  of  certain  factors  which  are  fundamental  and  essential  to  any  final 
and  satisfactory  investigation  of  the  facts. 

The  author  of  this  work  has  no  claim  to  speak  with  authority  as  a 
psychologist,  but  certain  principles  have  become  so  manifestly  evident  in  his 
own  field  of  investigation  that  he  assumes  the  liberty  to  advance  some  propo- 
sitions in  respect  to  investigations  of  visual  motor  processes,  covering  only 
certain  intrinsic  factors  which  have  been  conspicuously  absent  in  these  re- 
searches and,  lacking  which,  no  trustworthy  conclusions  can  be  reached. 

Only  two  of  the  most  noteworthy  of  these  neglected  factors  need  be  here 
mentioned:  — 

1.  No  reliable  results  can  be  attained  in  the  investigation  of  the  facts  of 
the  movements  of  the  eyes  in  space  perception  by  observing  the  action  of  eyes, 
the  condition  of  whose  motor  functions  have  not  been  positively  determined. 
In  the  reported  experiments,  one  who  is  expert  in  respect  to  the  anomalous 
states  of  the  motor  apparatus  of  the  eyes  will  detect  many  phenomena  which, 
by  the  investigators,  are  regarded  as  typical,  but  which  are  evidently  the  re- 
sults of  the  peculiarities  of  the  adjustments  of  the  eyes  of  the  subject  observed, 
that  is,  the  person  making  the  experiment.     To  repeat  an  illustration  which 
I  have  used  elsewhere,  as  well  might  a  surveyor  proceed  with  his  triangulations 
from   an  eminence  which  he  has  not  first  located  as  for  an  investigator  in 
visual  phenomena  to  assume  that  the  eyes  of  his  intelligent  subject  represent 
the  typical  movements  of  eyes  in  general. 

2.  While  psychologists  might  hardly  admit  that  the  element  of  attention 
has  been  absent  from  their  experiments,  it  is  evident  to  one  who  is  largely 


128  PHYSIOLOGY. 

occupied  with  visvial  phenomena  that  there  is  in  most,  if  not  in  all,  of  the 
experiments  recorded  a  notable  absence  of  any  adequate  means  for  fixing  the 
attention. 

To  illustrate :  If  a  point  of  light  swings  in  space  with  a  pendulum  move- 
ment, photographic  registration  shows  that  the  eye  follows  it,  not  in  an 
uninterrupted  and  regular  movement  corresponding  to  that  of  the  point  of 
light,  but  with  little  halts  and  forward  movements.  From  phenomena  of  this 
general  order  some  have  reasoned  that  this  is  the  typical  mode  of  motion  of 
the  eye  in  following  the  outline  of  an  object.  This  by  no  means  follows.  In 
such  a  monotonous  movement  of  the  object  it  is  unnecessary  and  somewhat 
difficult  for  the  eye  to  maintain  an  absolute  fixation.  It  is  easier  to  permit  the 
image  of  the  object  to  pass  out  of  the  region  of  the  fovea,  the  consciousness 
drawing  upon  the  faculty  of  estimating  its  position,  then  catching  up,  than 
to  hold  the  adjusting  apparatus  in  continuous  and  accurate  tension.  Were  the 
movements  of  the  point  of  light  more  complex,  such  as  could  not  be  assumed 
beforehand,  and  to  which  more  continuous  and  more  fixed  attention  would  be 
demanded,  it  is  safe  to  believe  that  the  movements  of  the  eyes  would  be  much 
more  in  correspondence  with  those  of  the  object.  The  principle  holds  in 
respect  to  investigations  with  certain  visual  illusions  that  an  impediment  to 
continuous  attention  to  a  line  of  movement  may  modify  the  extent  of  that 
movement.  By  practice  the  attention  may  be  more  definitely  confined  to  the 
object  to  be  examined,  and  hence  not  only  the  movement  of  the  eye,  but  the 
percept  of  space,  may  conform  more  nearlv  to  the  extent  of  the  object  viewed. 
It  is  an  error  to  attribute  this  correction  of  the  mental  estimate  of  space  to  an 
overcoming  of  a  mental  illusion.  It  is  the  result  of  the  ability  of  the  observer 
to  confine  his  attention  to  the  direct  line  of  extension  while  he  ignores  the 
hindering  objects  which  are  external  to  this  main  object,  refusing  to  permit 
the  attention  to  be  diverted. 

Devices  can  be  prepared  which  will  enable  an  investigator  to  be  assured 
that  the  attention  of  the  subject  is  continuously  fixed  upon  the  desired  object. 
Also,  with  a  complete  knowledge  of  the  personal  peculiarities  attending  the 
movements  of  the  eyes  of  the  person  under  observation,  more  exact  and  more 
satisfactory  investigations  can  be  undertaken  than  those  entered  upon  with 
the  assumption  that  the  eyes  of  every  intelligent  subject  must  be  subject  to 
the  laws  which  would  govern  in  a  typical  case. 

In  order,  then,  to  appreciate  size  by  the  sense  of  vision,  there 
must  be  movement  or  a  mental  conception  of  a  movement,  and  there 
arises  the  interesting  and  practical  question,  what  is  the  extent  of  the 
least  movement  which  can  be  interpreted  into  an  idea  of  size  and 
form. 

This  resolves  itself  into  the  question  of  the  space  over  which  the 
line  of  regard  must  move  in  order  to  recognize  magnitude.  And  at 
this  extreme  side  of  the  question  it  may  be  doubted  whether  the  prob- 
lem does  not  assume  a  somewhat  different  character. 

The  observations  of  Hook,  Weber,  Volkmann,  and  others  have 


VISUAL  PERCEPTION  OF  SPACE.  129 

resulted  in  an  acceptance  of  the  opinion  that  a  visual  angle  less  than 
from  50  to  75"  is  too  small  for  visual  appreciation,  but  that  a  space 
occupying  an  angle  equal  to  one  of  these  may,  under  favorable  circum- 
stances, and  with  a  good  eye,  be  perceived  as  space. 

It  happens  also  that  two  rays  of  light  entering  the  schematic  eye 
of  Listing  at  an  angle  of  73"  and  passing  to  the  retina,  would  there 
be  separated  0.0052  +  millimeter.  According  to  the  measurements  of 
Kolliker,  the  cones  at  the  macula  have  a  diameter  of  0.0045  millimeter. 
Thus  it  would  appear  that  the  smallest  movement  which  can  be  per- 
ceived is  about  that  which  would  be  required  to  move  the  ray  of  light 
from  one  cone  to  another.  The  question  whether,  in  case  the  cones 
were  much  smaller,  a  less  degree  of  motion  could  be  interpreted  by  the 
idea  of  space,  is  of  course  a  purely  speculative  one. 

It  was  on  the  basis  of  an  appreciation  of  space  by  a  movement  of 
the  eye  through  an  angle  of  60"  that  Snellen  constructed  his  system 
of  test  letters.  He  assumed,  however,  that  an  angle  of  5'  is  the  smallest 
at  which  characters  for  reading  can  be  clearly  made  out  by  the  average 
eye. 

In  researches  for  the  determination  of  the  role  played  by  the 
convergence  in  the  perception  of  distance  or  depth  many  experiments 
have  been  made,  two  only  of  which  need  here  be  mentioned.  Wundt1 
placed  the  face  before  a  box  open  at  that  side  and  having  a  horizontal 
slit  in  the  other  side  through  which  both  eyes  could  look  at  a  white 
screen,  all  surrounding  objects  being  shut  out  from  view.  A  vertical 
thread  kept  taut  by  a  weight  hung  between  the  slit  and  the  screen. 
In  experimenting  to  determine  to  what  degree  of  certainty  he  could 
estimate  the  comparative  distance  of  the  thread  when  it  was  made 
to  approach  or  recede,  he  was  careful,  whenever  the  thread  was  moved, 
to  close  the  eyes  during  the  movement  and  when  opening  them  to  look 
first  at  the  screen,  then  at  the  thread.  Wundt  found  that,  while  the 
degree  of  accuracy  increased  with  the  degree  of  convergence  of  the 
visual  lines,  on  the  average  he  could  determine  the  approximation  or 
the  recession  of  the  thread  within  1/50  of  the  distance.  For  example, 
if  the  thread  hung  at  50  centimeters  from  the  eyes  he  could  determine 
the  fact  that  it  was  nearer  when  the  thread  was  moved  up  to  49  cen- 
timeters. 

Professor  Bourdon2  has  made  still  more  exact  experiments.  His 
results  do  not  largely  vary  from  those  above  mentioned.  A  con- 


1  Lectures  on  Human  and  Animal  Psychology,  1894,  p.  151. 

2  La  Perception  Visuelle  de  1'  Espace,  1902. 


130  PHYSIOLOGY. 

vergence  of  8'  for  each  eye  with  the  fixed  object  at  1.08  meters  dis- 
tant was  necessary  to  recognize  the  fact  of  the  approach  or  the  reces- 
sion of  the  very  small  object.  The  fact  that  the  nature  of  the  change 
of  adjustment  of  about  one-fourth  of  a  degree  between  the  two  visual 
lines  could  be  almost  uniformly  detected  after  an  interval  of  time 
during  which  the  eyes  had  been  moved  in  various  directions,  indicates 
the  extreme  delicacy  of  the  sense  of  movement  of  the  visual  apparatus. 

It  will  be  seen  that  the  psychical  processes  in  vision  result  from 
definite  physical  actions,  and  that  the  character  of  the  perception 
received  in  vision  is  not  determined  so  much  by  the  picture  printed 
on  the  retina  as  by  the  movements  of  the  eyes,  although,  as  above 
remarked,  it  does  not  follow  that  the  line  of  sight  must  compass  every 
detail  of  the  figure  seen.  And  we  shall  see  presently  that  the  appa- 
rent size,  distance,  and  even  color  of  objects  are  influenced  largely 
by  processes  of  mind,  and  that  these  mental  processes  differ  in  char- 
acter under  different  circumstances.  Conclusions  drawn  from  experi- 
ences, contrasts,  comparisons  of  environment,  and  a  variety  of  psy- 
chical processes  enter  into  the  final  conception  upon  which  the  mind 
settles. 

By  excluding  to  too  great  an  extent  the  influence  of  these  purely 
psychical  elements  of  vision  and  confining  ourselves  to  the  examination 
wholly  of  physical  phenomena,  we  may  be  misled  in  regard  to  many 
of  the  facts  of  vision,  especially  those  relating  to  binocular  vision. 

Much  time  and  space  have  been  occupied  in  the  attempt  to  show 
why  the  reversed  image  imprinted  upon  the  retina  should  be  recog- 
nized by  the  brain  as  an  erect  image.  After  an  acceptance  of  the  view 
that  it  is  less  the  image  seen  than  the  motions  felt,  it  is  scarcely  neces- 
sary to  consider  the  retinal  picture,  nor  would  it  seem  important  to 
show  that  the  multitude  of  fibers  which  pass  from  the  elementary 
bodies  of  the  retina  back  to  the  brain  substance  are  not  so  arranged 
in  this  complicated  mass  of  cells  as  to  form  a  mosaic  in  the  receptive 
organ.  We  have  no  extensive  knowledge  of  the  course  and  destination 
of  these  fibers,  but  it  is  safe  to  presume  that  they  find  their  connec- 
tions with  the  brain  cells  not  in  any  plane  or  other  fixed  form  of  which 
we  have  any  conception,  and  that  in  the  brain  substance  there  is  no 
up  and  down,  right  or  left.  And  thus  it  is  that  the  notion  of  a  picture 
conveyed  to  the  brain  where  it  is  "felt"  or  perceived  is  an  evident 
hindrance  to  the  study  of  spatial  vision. 

It  is  true  that  owing  to  the  crossing  of  the  rays  in  reaching  the 
retina,  the  eye  in  following  the  outline  of  an  object  from  right  to 


VISUAL  PERCEPTION  OF  SPACE.  131 

left  must  move  from  right  to  left  and  in  following  it  from  above  down- 
ward must  also  move  downward,  yet  this,  in  the  light  of  the  considera- 
tions above  advanced,  would  seem  hardly  to  sustain  the  assertion  that 
because  of  the  reversal  of  the  image  and  the  consequent  movements 
of  the  eye  symmetrically  with  the  directions  of  the  outline  of  the 
object,  therefore  it  is  necessary  that  the  image  should  be  reversed.  An 
experienced  photographer  becomes  unconscious  of  the  reversal  of  the 
image  on  the  ground  glass  of  his  camera,  and  if  one  were  to  observe 
images  habitually  from  infancy  in  the  same  manner  we  have  no  reason 
to  suppose  that  the  fact  would  lead  to  disturbances  of  the  faculty  of 
localization,  although,  for  obvious  reasons,  it  would  be  attended  by  in- 
conveniences arising  from  the  resulting  positions  of  the  eye  in  limiting 
the  field  of  regard. 

It  has  been  said  above  that  in  obtaining  a  mental  conception  of 
the  form  of  an  object  in  space  the  eye  does  not  wander  aimlessly  on 
its  surface ;  it  in  fact  executes  movements  which  may  be  compared  to 
those  of  the  hand  if  it  were  to  pass  around  the  object  and  thus  by 
the  muscular  changes  resulting  in  the  hand  and  arm  conveying  to  the 
mind  an  idea  of  the  form  of  the  object.  Here  we  may  introduce  an- 
other comparison  between  the  psychical  results  obtained  by  the  move- 
ment of  the  eyes  and  those  of  the  hand  in  feeling  the  form  of  an 
object.  If  the  hand  should  be  passed  over  two  equal  surfaces,  for 
example,  two  squares  of  wood  of  equal  size,  one  of  which  is  perfectly 
smooth  while  the  other  is  marked  by  transverse  ridges,  the  smooth 
surface  would  appear  to  the  hand,  the  eyes  being  closed,  less  extensive 
than  the  ridged  surface  if  the  hand  pass  at  right  angles  with  the  ridges. 
In  like  manner,  if  the  hand  were  to  pass  first  in  the  longitudinal  direc- 
tion of  the  ridges  and  then  in  the  transverse  direction  of  the  same 
surface,  the  surface  would  not  seem  to  be  of  equal  dimensions  in  the 
two  directions,  but  of  greater  extent  in  the  direction  across  the  ridges. 

The  appreciation  of  the  apparent  size  of  objects  by  the  sense  of 
sight  may  be  modified  in  much  the  same  way. 

The  familiar  illustration  of  the  two  equal  squares,  one  marked  by 
horizontal,  the  other  by  vertical  lines,  will  help  to  impress  this  fact. 

In  Fig.  41  the  square  with  the  horizontal  lines  appears  notably 
higher  than  the  square  with  vertical  lines,  while  the  square  with  ver- 
tical lines  is  apparently  broader  than  the  other.  In  neither  case  do 
the  squares  seem,  as  they  really  are,  to  be  equal  on  all  sides. 

In  the  case  of  the  eyes,  as  in  that  of  the  hand,  the  single  effort 
of  sweeping  directly  from  one  extreme  of  the  object  to  the  other  with- 


132  PHYSIOLOGY. 

out  a  halt  or  an  obstacle  in  the  course  of  the  muscular  impulse  appears 
less  extended  than  the  effort  in  which  the  hand  or  the  eye  passes  from 
one  side  of  the  object  to  the  other  by  a  series  of  smaller  exertions.  It 
is  not  that  the  square  makes  a  larger  impression  along  the  horizontal 
meridian  of  the  retina  in  one  case  than  in  the  other,  but  that  repeated 
small  movements  appear  to  be  of  more  consequence  than  a  single  mus- 
cular sweep  of  equal  extent  to  the  sum  of  the  lesser  movements. 

Another  element  in  modifying  the  impression  of  the  extent  of  an 


Fig.  41. — Illusion  of  Height  and  Breadth. 

object  is  found  in  the  contrast  in  the  muscular  sense  between  an  action 
unimpeded  and  extended  beyond  the  point  of  measurement  to  be  de- 
termined and  an  action  suddenly  brought  to  a  close  and  turned  back 
upon  itself.  This  is  clearly  seen  in  the  figure  known  as  the  Muller- 
Lyer  illusion  (Fig.  42),  in  which  the  two  parts  of  the  horizontal  line 
are  of  equal  lengths,  yet  the  line  from  which  the  short  lines  diverge 


Fig.  42. — The  Miiller-Lyer  Illusion. 

in  the  direction  partly  continuous  with  the  main  line  appears  mate- 
rially longer  than  the  line  from  which  the  diverging  lines  turn  back- 
ward. 

In  the  first  case  the  eye  follows  along  the  course  of  the  ma'n 
line  and  encountering  the  diverging  lines  with  no  sudden  arrest  in  its 
course,  passes,  by  a  slight  modification  of  direction,  along  one  of  the 
diverging  lines.  In  the  opposite  case  in  the  movement  of  the  eye  the 
attention  is  diverted  to  the  retrograde  line,  and  the  movement  is  ar- 
rested before  the  extremity  of  the  long  line  is  reached. 


VISUAL  PERCEPTION  OF  SPACE. 


133 


If  one  should  leap  a  certain  distance  and  then  follow  the  leap 
with  some  steps  forward,  an  idea  of  the  distance  covered  by  the  leap 
would  result.  If  the  person  were  now  to  repeat  the  leap,  encountering 
an  obstacle  at  the  distance  of  the  first  leap  which  would  not  only  pre- 
vent further  advance  but  turn  him  back,  the  leap  in  the  first  instance 
would  seem  to  have  covered  a  greater  extent  than  the  second.  Experi- 
ments in  this  direction  may  be  varied  in  great  number,  showing  that 


Fig.  43. — After  Hering. 


Fig.  44. — After  Wundt. 

not  only  the  extent  but  the  direction  of  objects  in  the  field  of  view 
may  be  modified  to  the  consciousness  by  impressions  derived  from  the 
environments  of  the  object  seen. 

In  the  accompanying  two  figures  a  straight  line  does  not  appear 
as  a  straight  line  and  parallel  lines  do  not  appear  parallel. 

The  explanation  of  the  interesting  phenomena  shown  in  these 
diagrams  is  found  in  the  principle  already  cited,  that  if  a  movement 
be  continued  beyond  the  point  of  determination  the  distance  appears 


134 


PHYSIOLOGY. 


greater  than  if  the  movement  is  suddenly  arrested  and  turned  back. 
In  case  of  Fig.  43  the  angles  on  the  outer  sides  of  the  lines  permit 
the  movement  to  slide  without  sudden  arrest,  with  the  result  that  that 
side  of  the  long  line  appears  elongated,  and  the  line  also  approaches 
the  branching  lines,  not  because  the  picture  on  the  retina  brings  the 
long  line  in  closer  relation  to  the  branches,  but  because  in  the  move- 
ments required  the  two  lines  forming  the  acute  angles  are  brought 
in  relation  to  each  other  and,  as  Helmholtz  remarks,  there  is  the 
mental  contrast  of  the  angles  between  the  direct  and  the  oblique  lines. 
The  two  long  lines  appear  then  to  approach  toward  the  center 


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Fig.  45. — Zollner's  Figure. 

and  to  diverge  toward  the  extremities.  The  other  figure  shows  the 
angles  reversed,  with  the  effect  of  changing  the  apparent  curves  of  the 
really  straight  and  parallel  lines. 

The  principle  of  the  following  of  the  eye  along  the  line  of  the 
object  is  further  illustrated  by  the  diagram  of  Zollner  (Fig.  45),  in 
which  the  main  vertical  lines  appear  to  diverge,  the  divergence  being 
associated  with  the  special  direction  of  the  short  oblique  lines. 

Explaining  the  geometric  illusions  of  Hering  and  Wundt,  page 
133,  Hering  takes  the  ground  that  the  separation  of  two  points  removed 
from  each  other  by  a  small  distance  is  estimated  at  a  greater  relative 
value  than  that  of  points  farther  removed  if  there  is  no  dividing 


VISUAL  PERCEPTION    OF   SPACE.  135 

point  between  these  latter,  and  that  in  like  manner  a  small  arc  has 
a  larger  relative  value  than  a  greater  one  in  visual  perception.  Hence, 
in  the  figures  the  acute  angles  are  overestimated  and  the  obtuse  angles 
are  underestimated. 

Helmholtz  also  took  the  ground  that  these  illusions  are  examples 
of  the  rule  that  the  acute  angles  being  small  and  sharply  defined 
appear  in  general  relatively  too  great  when  compared  with  right 
angles  or  obtuse  angles  undivided. 

These  explanations  do  not  appear  to  reach  the  essential  and 
ultimate  reason,  for  we  must  ask  ourselves,  why  should  these  acute 
angles  be  overestimated? 

I  suggest  that  an  answer  to  this  last  question  may  be  found  in 
the  fact  that  the  movements  of  the  eye  for  the  acute  angle  are  incom- 
plete, while  for  the  obtuse  angles  they  are  more  in  conformity  with 
the  full  extent  of  the  lines  bounding  the  angles. 

Thus,  for  example,  if  the  line  of  sight,  by  movement  of  the  eye, 


passes  from  the  fixed  point  A  to  take  cognizance  of  the  angle  ABC, 
its  excursion  may  be  arrested  at  &'  and  pass  to  C.  Then,  since  the 
angle  Ab'C  is  greater  than  the  angle  ABC  this  latter  angle  is  over- 
estimated. 

This  hypothesis  is,  it  would  appear,  fully  sustained  by  the  inves- 
tigations of  Judd1  in  respect  to  the  Miiller-Lyer  illusion,  where  pho- 
tographic registrations  show  that  the  movement  of  the  eye  in  the 
direction  of  the  acute  angle  is  habitually  arrested  before  the  point  of 
the  angle  is  reached.  The  results  of  McAllister  on  the  fixation  of 
points  in  the  visual  field  and  those  of  Cameron  and  Steel  on  the 
Poggendorff  illusion2  seem  to  point  in  the  same  direction. 

In  respect  to  a  number  of  these  geometrical  illusions  Helmholtz 
also  regarded  the  phenomena  of  irradiation  as  a  sufficient  and  satis-  , 
factory  explanation  in  certain,  if  not  in  many,  cases,  and  he  pointed 


xYale  Psycholog.  Studies;    Psychol.  Review,  March   1905. 
2Loc.    nt. 


136 


PHYSIOLOGY. 


out  the  manner  in  which  these  phenomena,,  by  the  law  of  contrasts, 
might  induce  these  effects. 

In  a  more  recent  discussion  of  irradiation  as  the  cause  of  geomet- 
ric illusions,  Alfred  Lehmann1  illustrates  his  thesis  by  the  following 
figures  in  connected  squares  (Fig.  47),  and  asserts  that  the  illusion 
at  B  in  this  case,  must  be  entirely  due  to  irradiation. 

It  will  be  observed  that  the  two  lines  of  squares  at  B  appear  to 
incline  toward  each  other  above  and  to  recede  from  each  other  below, 
the  fine  connecting  line  being  transformed  into  a  series  of  zig-zags 
as  suggested  at  E.  He  argues  that,  in  this  case,  the  highly  and  the 
feebly  illuminated  spaces  are  in  close  juxtaposition,  permitting  irradia- 


D    B 


Fig.  47.  —  After  Lehmann. 


tion  from  the  clear  to  the  obscure  squares.  In  the  case  of  the  two 
series  of  squares  at  C,  the  connecting  line  is  so  broad  that  the  effect 
of  irradiation  does  not  extend  to  the  black  squares,  hence  there  is  no 
illusion.  On  the  other  hand,  at  A  where  there  is  no  strong  contrast 
in  the  illumination  of  the  squares,  the  illusion  is  also  absent. 

This  hypothesis,  as  Helmholtz  well  understood,  would  hardly 
apply  to  such  figures  as  the  Hering  illusions  (Figs.  43  arid  44),  or  to 
that  of  the  Miiller-Lyer  (Fig.  42)  ;  and  while  it  might  be  supposed 
that  the  Poggendorff  illusion  (Fig.  48),  when  the  upright  column 


1  Die     Irradiation     als     Ursache     geometrische-optischer     Tauschungen. 
Pfluger's  Archiv,  1904,  Bd.  103,  p.  84. 


PERSPECTIVE. 


137 


is  of  solid  black,  might  be  explained  on  this  principle,  it  can  hardly 
be  supposed  in  case  the  figure  is  drawn  in  outline  as  here  shown  that 
irradiation  can  be  an  important  factor  in  the  illusion. 

This  principle  of  illusions  of  geometric  forms  and  of  contrasts 
in  vision  is  a  practical  and  important  one,  too  little  considered  and 
as  a  rule  neglected.  It  applies  to  many  forms  of  art,  especially  to 
architecture,  to  drawing,  and  even  to  the  furnishing  and  tapestries  of 
private  and  public  rooms.  The  architect  who  plans  a  public  hall  for 
public  speaking  in  which  there  appear  lines  or  curves  which  induce 


Fig.  48. — Poggendorff  Illusion. 

illusory  impressions  such  as  have  been  mentioned,  draws  the  attention 
of  listeners  to  the  peculiarities  of  the  structure,  to  the  disadvantage 
of  both  hearers  and  speakers.  Even  the  carpet  on  the  floor  may,  by 
the  annoying  visual  impressions  to  which  it  gives  rise,  occupy  the 
attention  of  the  hearers  to  the  exclusion  of  subjects  supposed  to  be 
more  profitable. 


SECTION  XVI. 

PERSPECTIVE. 

Although  the  complete  idea  of  perspective  is  gained  only  by  the 
use  of  the  two  eyes,  there  are  yet  means  of  arriving  at  a  knowledge 
of  the  distance  of  objects  from  the  eye  which  are  furnished  by  monoc- 
ular vision.  We  have  already  seen  how,  as  the  eye  sweeps  from  one 
point  of  an  object  to  another,  or  from  one  object  to  another,  the  angle 
through  which  the  line  of  regard  passes  represents  an  extent  of  move- 


138  PHYSIOLOGY. 

ment  of  the  eye  in  respect  to  the  body,  or  the  extent  of  movement  of 
the  body  itself,  and  that  the  comparative  distance  of  the  points  or 
objects  from  each  other  in  the  field  of  vision,  is  measured  by  these 
movements.  Yet  there  is  in  this  statement  of  the  case  an  important 
omission,  for  a  comparatively  small  object  near  to  the  eye  will  occupy 
an  angle  in  the  field  of  regard  equal  to  the  angle  occupied  by  a  larger 
object  which  is  more  remote.  Hence  two  objects  of  unequal  size  may 
demand  equal  movements  of  the  line  of  regard,  in  order  to  sweep  from 
one  extremity  to  the  other  of  each,  and  hence  also  they  should  appear 
of  the  same  size.  We  find,  so  far  as  the  movements  of  the  eye  are  con- 
cerned, and  so  far  as  the  distance  of  the  points  of  the  retina  which 
correspond  to  the  extreme  points  of  the  two  objects  are  concerned, 
they  are  seen  as  though  of  equal  size.  Yet  there  is  a  consciousness  that 
these  objects  are  not  of  like  dimensions,  and  this  consciousness  arises 
from  the  knowledge  that  one  of  the  objects  is  removed  to  a  greater 
distance  from  the  eye  than  the  other.  We  may  then  say  that  in  order 
to  give  a  correct  impression  of  the  comparative  size  of  objects  in  the 
field  of  view,  there  must  be  not  only  a  knowledge  of  the  superficial 
extent  of  the  images  of  these  objects,  but  a  knowledge  of  depth  or 
distance. 

This  knowledge  of  distance  from  the  eye  is  acquired  by  the  ex- 
perience of  the  individual  in  regard  to  the  size  of  familiar  objects, 
through  the  efforts  made  in  accommodation  of  the  eye,  by  comparison 
of  the  size  of  unfamiliar  with  familiar  objects,  and  largely  through 
the  simultaneous  use  of  the  two  eyes.  For  the  present  we  are  to  con- 
sider only  the  means  of  judgment  afforded  by  a  single  eye.  Among 
these  means  are  those  employed  by  an  artist  who  spreads  a  picture 
upon  a  canvas.  It  is  a  matter  of  small  consequence,  so  far  as  the 
merits  of  the  picture  are  concerned,  whether  it  represents  the  objects 
included  on  a  large  or  a  small  scale,  if  the  relative  proportions  of  size 
are  maintained.  In  the  picture  the  relative  distance  is  suggested  by 
the  shadows,  and  by  the  relative  size  of  familiar  objects.  Thus  in 
many  pictures  it  is  essential  that  figures  of  persons  or  of  domestic  ani- 
mals be  introduced,  in  order  to  convey  any  just  idea  of  the  size  of  the 
principal  objects  represented. 

It  is  possible  within  certain  limits  for  those  in  whom  the  function 
of  accommodation  is  active,  to  judge  of  the  comparative  distance  of 
different  objects  along  the  line  of  regard.  The  limits  of  this  means 
are  narrow,  for  beyond  a  certain  distance,  a  few  feet  only,  the  accom- 
modation is  not  an  element  of  importance,  and  even  until  the  object 


PERSPECTIVE. 


139 


is  almost  within  the  reach  of  the  hand,  the  influence  of  accommoda- 
tion is  only  plainly  perceptible  for  considerable  differences  of  dis- 
tance. Of  course,  after  a  certain  age  the  accommodation  plays  no 
essential  part  in  the  estimation  of  distances. 

Such  comparisons  are,  of  course,  the  result  of  experience.  An 
infant,  having  little  experience,  reaches  out  for  objects  unattainable. 
Distant  objects  appear  to  the  child  small,  not  distant. 

The  relation  of  objects,  as  shown  by  the  partial  hiding  of  one  by 
the  other,  serves  as  a  means  of  comparison.  If  a  tree  of  a  certain 
kind  stands  in  front  of  a  hill  so  as  to  conceal  a  part  of  it,  the  tree  must 
be  nearer  to  the  eye  than  the  hill,  and  from  a  knowledge  of  the  usual 
height  of  a  tree  of  the  kind  when  it  has  attained  to  a  certain  form,  we 
may  judge  of  the  object  behind  it.  If,  however,  an  artist  were  to  draw 


Fig.  49. — Schroder's  Diagram. 

a  hill  behind  a  plant  of  an  unknown  species,  no  judgment  of  the  ele- 
vation of  the  hill  could  be  formed  from  the  comparison. 

The  perspective  of  such  objects  as  surround  us  in  our  houses — 
tables,  chairs,  stairways,  doors,  etc. — is  easily  recognized  usually  by 
the  angles  formed  by  the  line  of  regard  and  the  object  which  is  seen 
or  the  picture  which  is  drawn  of  it.  If  the  angles  are  such  that  they 
may  apply  to  the  object  in  more  than  a  single  position,  the  distances 
of  the  various  parts  may  not  be  uniformly  interpreted  from  a  diagram, 
unless  there  is  added  the  normal  shading  by  which  the  relative  posi- 
tions become  fixed  in  the  mind.  The  diagram  of  Schroder1  (Fig.  49), 


1  "Poggendorff's  Annalen,"  cv,  shown  in  Helmholtz,  "Optique  Physio- 
logique."  Looking  at  the  diagram  the  idea  of  a  flight  of  stairs  against  a  wall 
is  suggested,  but  if  the  diagram  is  still  further  examined  it  appears  as  a  piece 


140  PHYSIOLOGY. 

which  permits  a  different  interpretation,  depending  on  the  choice  of 
a  line  as  the  near  or  distant  one,  illustrates  the  principle  that  such 
diagrams  must  have  certain  individual  characteristics  in  order  to 
present  uniformly  to  the  mind  the  same  idea. 

The  character  of  illumination  of  an  ohject  often  influences  the 
mind  in  determining  the  quality  of  depth  or  of  relief,  and  it  is  not 
infrequently  the  case  that  of  two  objects  or  two  parts  of  one  object 
which  are  at  some  distance  from  the  eye,  that  having  the  strongest 
illumination  will  appear  less  remote  than  the  other.  The  effects  of 
shades  become,  in  the  hands  of  a  skillful  artist,  his  most  important  aids 
in  giving  to  his  canvas  the  appearance  of  nearness  and  distance,  of 
foreground  and  background ;  and  even  the  comparative  size  of  objects 
in  the  picture  is  often  determined  by  the  length  or  position  of  the  shad- 
ows. In  the  actual  view  of  objects  the  same  principles  hold,  for  the 
artist  only  copies  from  Nature  the  effects  of  perspective  which  are 
afforded  by  the  shadows. 

Again,  the  comparative  dimness  with  which  objects  are  seen  at 
a  great  distance,  in  contrast  with  the  brightness  of  objects  more  nearly 
situated,  forms  another  element  in  the  mental  estimate  of  relative 
distances. 

A  universal  subject  of  speculation  with  writers  who  treat  of  per- 
spective is  the  apparent  size  of  the  moon  when  seen  near  the  horizon 
and  when  it  appears  near  the  zenith.  That  in  the  first  position  it  ap- 
pears larger  than  in  the  second,  is  well  known,  but  the  reasons  for 
the  phenomenon  given  by  various  writers  have  not  all  been  in  harmony. 

When  objects  are  at  an  infinite  distance,  there  is  no  direct  means 
of  judging  of  the  comparative  size.  Of  two  stars  which  may  appear 
of  the  same  size,  one  may  be  a  planet  of  our  system,  the  other  a  sun 
equal  to  many  such  planets.  Yet  on  account  of  the  comparative 
proximity  of  the  moon,  we  may  form  an  estimate  of  its  apparent 
size  under  various  circumstances.  Helmholtz  supposes  that  the  aerial 
perspective,  that  is  the  dimness  produced  by  the  great  extent  of  air, 
to  which  allusion  has  just  been  made,  furnishes  an  explanation.  An 
object  occupying  the  same  visual  angle  at  the  two  positions,  but  seen 
through  a  greater  extent  of  air  at  the  horizon  than  at  the  zenith,  and 


of  overhanging  wall  with  graded  shelvings.  When  one  of  these  impressions 
has  taken  possession  of  the  mind  it  is  difficult  to  change  to  the  other  im- 
pression. Yet  suddenly  the  change  is  made,  when  it  is  as  difficult  to  return 
to  the  first  impression. 


PERSPECTIVE.  141 

therefore  less  sharply,  appears,  according  to  him,  larger  from  the  asso- 
ciation of  ideas  arising  from  daily  experience. 

While  this  may  be  and  doubtless  is  an  element  in  the  solution  of 
the  question,  there  is  probably  another  equally  important  if  not  more 
influential.  It  is  in  the  position  of  the  eye  when  looking  at  the  object 
in  the  different  positions.  We  are  accustomed,  when  looking  at  remote 
objects,  to  raise  the  eyes.  With  the  idea  of  elevating  the  line  of 
regard  comes  the  idea  of  distance,  and  with  it  that  of  smallness. 
The  association  of  ideas  is  somewhat  complicated,  and  will  be  better 
understood  when  the  section  on  "Unconscious  Conclusions"  is 
considered. 

The  elements  in  the  conception  of  the  third  dimension  which  we 
have  thus  far  studied,  are  those  which  may  be  obtained  by  the  use  of 
a  single  eye.  They  consist  in  some  degree  of  efforts  of  accommodation, 
but  more  largely  of  movements  of  the  line  of  regard,  governed  by 
contrasts  of  color  and  of  light  and  shade,  and  are  for  the  most  part 
such  as  can  be  represented  by  a  painter  upon  canvas.  The  apprecia- 
tion of  the  meaning  of  the  various  arrangements  of  light  and  shade 
and  of  size  and  relative  position  of  these  color  surfaces  upon  a  canvas 
must  of  necessity  be  the  result  of  experience.  There  can  be  no  innate 
conception  of  the  resemblance  of  the  picture  of  a  landscape  to  the 
landscape  itself,  for  there  is  no  essential  resemblance  between  the  two. 
The  picture  consists  of  signs  which  are  interpreted  by  the  mind  in 
accordance  with  the  various  movements  of  the  line  of  regard  in  rela- 
tion to  the  lights  and  shadows  of  the  picture  and  the  accordance  of 
these  movements  and  these  contrasts  of  light  and  shade  with  the 
ordinary  experience  in  viewing  the  real  landscape. 

In  considering  the  elements  of  the  visual  conception  of  the  third 
dimension  thus  far,  we  have  supposed  the  eye  to  be  in  a  single  and 
unvarying  position,  modified  only  by  the  movements  necessary  to 
enable  the  line  of  regard  to  sweep  over  the  different  points  of  the  field 
of  view. 

An  element  of  great  importance  may  be  added  to  these,  in  a 
change  of  position  of  the  eye  itself,  so  that  the  object  may  be  seen 
from  different  points  of  view.  Thus  by  a  movement  of  the  head,  or 
by  a  change  of  position  of  the  body,  there  may  be  added  to  the  im- 
pressions which  have  already  been  discussed  new  impressions  of  im- 
mense importance  in  the  formation  of  the  conception  of  perspective. 
In  this  case  the  mind,  carrying  the  impression  received  from  the  first 
position,  adds  this  impression  to  that  which  is  received  in  the  new 


142  PHYSIOLOGY. 

position,  and  thus  forms  a  more  perfect  idea  of  relief  than  was  pos- 
sible while  the  objects  were  seen  from  a  single  point  in  space  only. 

A  new  element  in  forming  the  conclusion  also  enters  with  the 
displacement  of  the  eye  relative  to  the  object  seen,  for  not  only  is  the 
object  itself  seen  from  different  points  of  view,  but  if  the  object  is 
at  a  finite  distance,  all  surrounding  objects  undergo  an  apparent 
change  of  position  relative  to  the  object  regarded.  If  the  other  ob- 
jects are  at  a  greater  distance  from  the  eye  than  that  which  is  fixed 
by  the  eye,  the  displacement  of  those  objects  will  be  in  a  direction  the 
reverse  of  the  change  of  position  of  the  eye  itself.  If  they  are  nearer 
than  the  object  fixed,  they  will  move  in  the  same  direction  as  the  eye. 
Such  relative  changes  in  the  apparent  position  of  objects  becomes  a 
most  important  means  of  determining  their  relative  distances,  and 
without  these  changing  angles,  perspective  is  deprived  of  its  most 
effective  aid. 

If  this  change  of  position  of  the  eye  through  the  movement  of 
the  head  or  body  brings  such  material  assistance  to  the  conception  of 
perspective  by  the  mental  comparison  of  the  impressions  received  at 
successive  moments  of  time,  much  more  may  we  look  for  even  greater 
assistance  in  this  conception  when  two  eyes,  governed  by  the  same  will, 
and  carrying  impressions  to  the  same  sensorium,  and  which  are  situ- 
ated at  some  distance  from  each  other,  receive  simultaneous  impres- 
sions from  the  objects  within  the  field  of  regard.  In  this  case  there 
are  presented  to  the  mind  simultaneous  impressions  of  contrasting 
shadows  and  relative  angles  which  can  be  instantly  and  accurately 
compared,  and  the  results  of  experience  brought  into  service  while  all 
the  elements  for  forming  the  conception  are  present.  By  this  means 
the  ideas  of  distance  may  be  accurately  and  quickly  acquired. 

Binocular  vision,  therefore — simultaneous  vision  with  the  two 
eyes — becomes  a  study  of  first  importance. 

Coming  to  the  study  of  distance  and  of  relief  by  binocular  vision 
we  have  the  elements  for  forming  the  judgment  which  we  have  already 
recognized  in  the  case  of  using  one  eye  only,  to  which  a  number  of 
very  important  elements  are  added.  In  the  recognition  of  distance  and 
relief  one  must  appreciate  not  only  the  absolute  distance  of  the  object, 
but  the  comparative  distances  of  its  different  parts. 

This  may  be  arrived  at,  first,  by  a  comparison  of  the  outlines 
of  the  object  as  seen  by  the  two  eyes  if  the  object  is  at  a  finite  distance, 
for,  owing  to  the  difference  of  direction  of  the  lines  of  regard,  the  form 
of  the  images  recognized  by  the  two  eyes  may  not  be  the  same,  and 


THE  STEREOSCOPE.  143 

this  difference  of  outline  is  quickly  appreciated  by  the  consciousness. 
Second,  the  direction  in  which  upright  lines  appear  to  lean  as  seen 
by  eacli  eye.  Third,  the  distribution  or  the  extent  of  lights  and 
shades  may  be  unlike  for  the  two  eyes.  Fourth,  the  relation  of  the 
object  to  objects  behind  or  in  front  of  it  differs  for  the  two  eyes. 
Fifth,  the  sense  of  comparative  convergence.  Sixth,  the  difference 
presented  to  the  two  eyes  in  the  apparent  height  of  different  parts 
of  the  object  which  may  be  of  the  same  height.  These  and  some  other 
principles  which  enter  into  the  subject  can  best  be  examined  by  the 
aid  of  the  stereoscope  and  hence  it  is  convenient,  before  entering  more 
in  detail  upon  the  study  of  the  phenomena  of  binocular  vision,  to 
investigate  the  mechanism  and  principle  of  the  stereoscope  as  the  in- 
strument which  affords  the  most  important  aid  in  that  study. 

SECTION  XVII. 

THE  STEREOSCOPE. 

It  was  Wheatstone,  afterward  Sir  Charles  Wheatstone,  who  in 
1833  first  enunciated  the  principle  on  which  the  stereoscope  is  con- 
structed. He  had  put  into  practical  application  the  vague  ideas  of 
binocular  vision  which  had  from  time  to  time  been  suggested  by 
Euclid,  Galen,  Leonardo  da  Vinci,  and  in  later  times  somewhat  more 
in  detail  by  others,  and  was  able  to  show  that  by  placing  before  the 
eyes  two  pictures,  differing  as  the  impressions  of  natural  objects  differ 
when  received  by  the  two  eyes,  a  single  picture  with  the  idea  of  relief 
was  then  obtained. 

His  enunciation  was  as  follows :  "A  solid  object  being  so  placed 
as  to  be  regarded  by  both  eyes  projects  a  different  perspective  figure 
on  each  retina;  now,  if  these  two  perspectives  be  actually  copied  on 
paper  and  presented,  one  to  each  eye  so  as  to  fall  on  corresponding 
parts,  the  original  solid  figure  will  be  apparently  represented  in  such 
a  manner  that  no  effort  of  the  imagination  can  make  it  appear  as  a 
plane  surface." 

The  stereoscope  of  Wheatstone  consisted  of  two  glass  mirrors  fixed 
in  frames  and  adjusted  to  an  angle  of  90°  with  each  other.  In  a  panel 
at  each  side,  at  an  angle  of  45°  with  the  mirror  of  the  same  side,  the 
drawings  are  placed.  The  image  of  each  drawing  received-  by  its  re- 
spective mirror  is  reflected  toward  the  position  at  which  it  is  to  be 
received  by  the  eye.  By  means  of  mechanical  arrangements  the  pic- 


144 


PHYSIOLOGY. 


tures  may  be  moved  to  a  greater  or  less  distance  from  the  mirror 
and  also  their  angle  to  the  mirror  may  be  changed. 

Thus  the  two  pictures  may  be  presented  to  the  eyes  when  ad- 
justed in  parallelism  or  in  convergence.  The  diagram  (Fig.  50)  rep- 
resents the  principles  of  the  reflecting  stereoscope. 


Fig.  50. — Diagram  representing  the  principle  of  Wheatstone's  Stereoscope. 
a,  a,',  The  cards  with  the  two  pictures,  ft,  &',  The  mirrors,  c,  c',  The  appa- 
rent position  of  the  combined  images. 


The  possibility  of  viewing  the  stereoscopic  images  with  the  visual 
lines  parallel  renders  this  form  of  instrument  more  serviceable  in  ex- 
periments with  binocular  vision  than  the  form  now  in  most  general 
use  and  which  is  now  to  be  described. 

This,"  the  commonly  known  stereoscope,  is  the  modification  of 
Brewster  and  is  known  as  the  refracting  stereoscope.  Essentially  it 
consists  of  two  prisms  whose  apices  are  turned  toward  each  other. 


THE  STEREOSCOPE. 


145 


These  prisms  are  sufficiently  strong  to  bring  two  pictures  whose  cor- 
responding parts  are  two  and  a  half  inches  distant  from  each  other 
to  coincide  at  the  required  distance  from  the  lenses.  A  screen  sep- 
arates the  two  prisms  and  extends  forward  so  as  to  shut  out  the  left 
image  from  the  right  eye  and  the  right  image  from  the  left  eye.  In 
practice  the  prisms  are  compound  lenses,  combining  with  the  pris- 
matic element  a  convex  spherical  curve  by  which  the  pictures  are 
somewhat  enlarged.  By  carrying  the  pictures  to  a  greater  or  less  dis- 
tance from  the  glass  the  focus  may  be  adjusted  for  different  eyes. 
Fig.  51  illustrates  the  principle  of  the  Brewster  stereoscope. 


Fig.  51. — Brewster's  Stereoscope. 

Recognizing  some  of  the  defects  of  the  refracting  stereoscope  of 
Brewster  as  an  instrument  in  the  study  of  physiological  optics,  yet 
appreciating  the  advantages  of  its  form  over  that  of  the  reflecting 
stereoscope  of  Wheatstone,  Helmholtz  constructed  a  stereoscope  in 
which  the  lenses,  mounted  in  tubes,  could  be  raised  or  lowered  and 
carried  in  or  out.  This  stereoscope,  although  useful  in  physiological 
investigations,  was  not  introduced  into  general  use. 

Another  stereoscope,  on  a  principle  combining  prisms  and  mir- 
rors, was  called  by  him  the  telereoscope.  This  instrument  was  de- 
signed to  obtain  the  effect  of  relief  at  great  distances,  and  in  order  to 
reach  this  result,  the  base  line  between  the  points  receiving  the  two 


146  PHYSIOLOGY. 

images  was  made  greatly  to  exceed  the  base  line  between  the  eyes. 
Each  eye  looks  into  its  respective  tube,  from  which  it  receives  the 
image  which  has  first  encountered  the  mirror  and  has  been  reflected  by 
it  along  the  horizontal  tube  until  it  is  refracted  by  the  prism  into  the 
short  tube  containing  the  ocular.  The  object  is  thus  seen  as  from 
two  points  removed  as  far  as  from  one  extremity  of  the  instrument  to 
the  other. 

By  recent  modifications  of  this  principle,  field  glasses  of  greatly 
improved  stereoscopic  effect  are  now  manufactured. 

By  means  of  the  stereoscope  many  of  the  phenomena,  of  binocular 
vision  may  be  so  represented  as  to  permit  of  analysis  and  comparison 
such  as  could  not  be  controlled  in  ordinary  binocular  vision,  and  the 
knowledge  of  this  subject  may,  in  fact,  be  said  to  have  dated  from 
the  invention  of  Wheatstone. 

If  two  symmetrical  or  nearly  symmetrical  diagrams  are  drawn 
upon  a  piece  of  cardboard,  at  a  distance  about  equal  to  that  separating 
the  two  eyes,  and  the  cardboard  being  held  parallel  to  the  base  line 
uniting  the  eyes  and  directly  in  front,  the  images  of  these  two  dia- 
grams may  be  made  to  unite  and  appear  as  a  single  image.  If  the  two 
diagrams  are  symmetrical  in  form  and  position,  the  united  image  will 
be  similar  to  each  of  the  two  original  diagrams,  but  if  there  is  slight 
asymmetry  in  form  or  position,  the  combined  image  will  differ  from 
both  the  originals,  and  will  assume  some  features  essentially  different 
from  either. 

This  experiment  may  be  made  in  the  following  manner: — 

Make  any  diagram,  however  simple.  It  may  be  two  straight  lines 
only,  but  situated  at  a  distance  apart  equal  to  the  nodal  points  of  the 
two  eyes.  Let  the  direction  of  the  two  lines  vary  slightly,  as  in 
Fig.  52. 

Holding  the  card  directly  in  front  of  the  observer,  the  visual  lines 
are  held  in  parallelism,  but  the  accommodation  is  adjusted  for  the 
distance  of  the  card.  For  those  who  are  not  practiced  in  the  control 
of  the  eyes  for  optical  experiments,  it  may  be  necessary  to  introduce 
some  assistance,  either  in  the  form  of  a  card  which,  being  placed  in 
the  median  line,  prevents  the  crossing  of  the  visual  lines,  or,  still 
better,  the  experimenter  may  use  a  tube  of  a  few  inches  in  length, 
which  he  holds  in  the  hand  before  one  eye,  and  directs  it  toward  dia- 
gram of  the  corresponding  side.  Two  such  tubes  may  be  used,  one 
before  each  eye.  After  some  practice  with  the  tubes,  removing  one 


THE  STEREOSCOPE.  147 

and  then  the  other,  the  knack  of  blending  the  figures  may  be  acquired.1 
It  is  much  less  easy  for  persons  who  have  either  esophoria  or  ortho- 
phoria  to  accomplish  this  than  for  those  who  have  a  moderate  degree 
of  exophoria. 

Another  method  of  blending,  and  one  much  more  easily  acquired 
than  that  just  mentioned,  is  to  cross  the  eyes  (the  right  eye  being 
directed  to  the  left  image,  and  vice  versa],  so  as  to  bring  the  com- 
bined image  to  the  point  of  crossing  of  the  visual  lines.  In  this  case 
the  combined  image  will  appear  nearer  than  the  two  originals,  and 
the  eyes,  instead  of  being  in  parallelism,  are  in  convergence.  The 
perspective  is  in  this  case  reversed,  so  that  pictures  and  diagrams  have 
not  the  usual  appearance  of  relief,  but  the  parts  of  the  diagram  which 
should  appear  in  advance  will  seem  to  be  behind. 


Fig.  52. 

In  the  experiment  (Fig.  52)  the  combined  image  will  assume  a 
direction  different  from  either  of  the  original  diagrams.  It  will  lean 
neither  to  the  right,  like  the  left  object,  nor  to  the  left,  like  the  right 
one.  If  combined  with  the  visual  lines  parallel,  as,  for  example,  when 
looking  through  the  mailing  tubes,  it  will  lean  with  its  upper  end 
approaching  the  observer,  while  if  the  union  is  made  by  converging 
the  eyes,  the  upper  end  will  appear  remote,  and  the  lower  end  will 
approach  the  observer.  With  the  stereoscope  the  leaning  will  be  in 
the  direction  seen  with  the  mailing  tubes. 

In  all  experiments  of  this  class,  such  as  those  made  by  Volkmann, 


1For  the  experiments  in  this  section  and  in  that  on  "Unconscious  Con- 
clusions." the  reader  would  do  well  to  supply  himself  with  two  tubes  known 
as  "mailing  tubes,"  which  can  be  procured  at  most  stationers  at  a  very  small 
expense. 


148  PHYSIOLOGY. 

Helmholtz,  and  others,  in  respect  to  corresponding  lines  and  points 
of  the  retina,  it  is  essential  to  know  whether  the  blending  is  effected 
by  one  or  the  other  of  the  methods  just  described,  for  if  by  the  first 
method,  the  visual  lines  are  supposed  to  be  parallel,  while  by  the  sec- 
ond, those  lines  must  be  in  convergence,  and  all  tests  might  undergo 
an  important  modification,  depending  on  the  fact  of  convergence  or 
not. 

If  we  inquire  why  the  two  lines  in  the  experiment  blend,  with  the 
appearance  of  leaning,  not  to  one  or  the  other  side,  but  from  or  toward 
the  observer,  according  to  the  method  of  blending,  the  answer  is  that 
the  two  lines  of  the  diagram  represent  the  apparent  position  of  an 
object  which  would  lean  as  seen  in  the  blended  image,  if  the  object 
were  viewed  separately  by  each  eye. 

If  a  pencil  or  rod  is  held  in  the  hand,  in  front  of  the  eyes,  and 
made  to  lean  with  its  upper  extremity  toward  the  observer,  then  if 
the  two  eyes  are  closed  alternately,  it  will  be  seen  that  the  pencil  does 
not  appear  to  lean  backward  so  much  as  from  side  to  side,  according 
to  the  eye  which  sees  it.  If  the  right  eye  is  closed,  and  the  left  is 
directed  to  the  pencil,  it  appears  to  lean  to  the  right,  and  if  the  left 
eye  is  closed,  the  leaning  is  reversed.  Now  if  we  combine  in  the  mind 
these  two  impressions,  we  have  the  effect  of  binocular  vision,  and  the 
two  lines  of  the  diagram  represent  in  their  positions  the  positions  of 
a  real  object  leaning  away  from  us,  as  seen  by  the  two  eyes. 

Hence  stereoscopic  pictures  are  such  as  would  be  seen  if  the  object 
were  looked  at  first  with  one  eye  and  then  with  the  other.  And  inas- 
much as  they  thus  render  the  various  lines  of  the  picture  from  the 
direction  of  the  two  eyes,  the  mind  accepts  the  two  pictures  as  though 
the  real  object  were  viewed  binocularly. 

A  second  experiment  of  a  simple  character  will  introduce  another 
fundamental  form  of  stereoscopic  images: — 

Hold  two  pencils  or  rods,  one  in  the  right  hand,  vertically,  in 
front  of  the  right  eye,  and  at  a  distance  of  about  fifteen  inches ;  the 
other  also  vertically,  and  in  front  of  the  left  eye,  at  the  distance  of 
eighteen  inches.  Now,  if  the  right  and  left  eyes  are  closed  alter- 
nately, it  will  be  seen  that  when  the  right  eye  is  closed,  the  interval 
between  the  two  rods  is  greater  than  the  interval  when  the  left  eye  is 
closed  and  the  right  eye  is  directed  toward  the  two  objects.  If  we 
would  imitate  this  phenomenon  on  a  stereoscopic  card,  we  would  rep- 
resent the  two  vertical  rods  by  two  vertical  lines  on  each  end  of  the 
card,  but  the  interval  between  the  lines  on  the  left-hand  end  of  the 


THE  STEREOSCOPE. 


149 


card  would  be  greater  than  that  between  the  lines  at  the  right-hand  end 
of  the  card.  If  now  we  accomplish  a  blending  of  these  two  couplets 
of  lines,  they  will  appear  to  the  observer  to  have  the  same  relative 
positions  as  the  two  rods  in  the  first  part  of  the  experiment,  that  is,  the 
left  vertical  line  will  appear  most  distant. 

As  it  will  be  seen  in  the  section  devoted  to  the  treatment  of 
strabismus,  the  stereoscope  has  of  late  come  into  somewhat  extensive 
use  for  reestablishing  and  preserving  the  vision  of  the  amblyopic  stra- 
bismic  eye.  To  this  end  a  number  of  forms  of  the  instrument  have 
been  devised,  of  which  we  mention  only  that  proposed  by  Prof.  E. 
Landolt,  of  Paris.1 


Fig.   53. — Landolt's   Stereoscope  for  Reestablishing  Binocular   Vision. 

Professor  Landolt  says,  the  principal  difficulty  in  attempts  to  re- 
establish binocular  vision  (in  strabismus)  is  found  in  the  predomi- 
nance of  the  visual  impressions  of  the  good  eye.  He  therefore  resorts 
to  the  expedient  of  reducing  the  visual  acuity  of  the  good  eye  by  mak- 
ing a  screen  pass  rapidly  before  it  while  the  image  presented  to  the 
amblyopic  eye  is  of  great  luminosity.  For  this  purpose  he  uses  a 
stereoscope  composed  of  two  tubes  (Fig.  53)  about  12  centimeters 
long,  which  are  joined  by  a  ball  and  socket  joint.  Each  tube  has  a 
convex  lens  as  an  ocular,  the  focus  of  which  coincides  with  the  length 
of  the  tube.  At  the  further  extremities  are  placed  plaques  which 


1  "Un  Nouveau  Stereoscope  Destin§  au  Retablissment  de  la  Vision  Bi- 
noculaire."  Proceedings  International  Congress  of  Opthalmology  at  Utrecht, 
1899,  page  86. 


150 


PHYSIOLOGY. 


carry  the  stereoscopic  figures.  They  are  to  be  viewed  by  strong  illu- 
mination and  are  photographed  on  ground  glass. 

The  intensity  of  the  image  of  the  good  eye  is  reduced  at  will  by 
superimposing  glasses  of  somber  tint  in  number  sufficient  to  equalize 
the  visual  impressions  of  the  two  eyes  and  thus  facilitate  the  union 
of  their  images.  This  may  also  be  done  gradually  by  an  iris  dia- 
phragm. 

Exercises  are  commenced  by  attempts  to  unite  the  most  simple 
figures  while  the  image  of  the  best  eye  is  caused  to  appear  and  dis- 
appear in  rapid  succession  while  the  object  is  constantly  presented  to 
the  poor  eye. 


Fig.  54. — The  Stereostroboscope. 


THE  STEREOSTROBOSCOPE. 

With  the  view  of  representing  objects  in  relief  by  several  pictures 
presented  to  the  two  eyes  in  succession  a  number  of  instruments  have 
been  devised  to  which  the  name  stereostroboscope  has  been  applied. 

In  the  stereostroboscope  the  eyes  converge  for  one  point,  but  do 
not  simultaneously  see  the  point.  The  principles  of  Miinsterberg's 
instrument1  may  be  briefly  stated  thus:  Looking  toward  a  disc,  B 
(Fig.  54)  on  which  are  successive  stereoscopic  figures  at  equal  distance 
from  the  margin  and  from  each  other,  the  observer  sees  through 


l"A   Stereoscope  Without  Mirrors   and  Without  Prisms,"  Psychological 
Revew,  I,  56,  1894. 


THE  PSEUDOSCOPE.  151 

another  disc  A,  large  enough  to  screen  the  first,  through  which 
are  cut  slits  in  two  radial  series  so  placed  that  the  right  eye  sees 
through  one  series  when  the  disc  is  rotated,  the  left  through  the 
other  series.  The  slits  for  the  right  and  left  eve  do  not  present 
themselves  simultaneously,  but  alternately.  The  two  discs  are  caused 
to  rotate  with  each  other.  As  the  pictures  are  presented  to  the  eyes 
alternately  and  as  these  pictures  have  alternately  the  characteristics 
of  stereoscopic  pictures  the  result  is  similar  to  the  combined  images 
with  the  stereoscope.  To  certain  persons  who  find  the  union  of  the 
pictures  with  the  stereoscope  difficult  or  impossible,  the  stereostrobo- 
scope  affords  a  substitute  by  which  they  are  enabled  to  obtain  the 
effects  which  are  familiar  to  others. 


THE  PSEUDOSCOPE. 

In  the  case  of  the  stereoscope  the  pictures  seen  by  the  two  eyes 
conform  in  shape  and  proportions  to  the  images  seen  by  the  corres- 
ponding eyes  when  an  object  of  three  dimensions  which  they  are 
intended  to  represent  is  seen  in  binocular  vision. 

A  confirmation  of  the  principles  of  the  stereoscope  is  found  when 
the  conditions  of  seeing  are  reversed.  For  example,  if  the  image  of 
that  side  of  the  object  which  is  ordinarily  recognized  by  the  right 
eye  should  be  presented  to  the  left  and  that  for  the  left  presented  to 
the  right  eye,  the  object  which  should  be  seen  in  relief  is  perceived  in 
intaglio.  Also,  if  the  course  of  the  rays  of  light  as  they  enter  each 
eye  is  so  changed  that  those  rays  which  would,  under  ordinary  cir- 
cumstances, fall  at  the  outer  side  of  the  point  of  clearest  seeing, 
should  be  diverted  to  the  inner  side,  and  vice  versa,  the  result  will 
be  the  conversion  of  the  relief  into  that  of  depression,  since  the  inter- 
pretations are  changed  by  the  inversion  of  the  points  impressed  in 
the  two  fields  of  vision. 

Such  reversion  of  the  course  of  the  rays  may  be  traced  in  Wheat- 
stone's  pseudoscope  (Fig.  55),  where  the  rays  from  the  points  A  and 
B  are  caused  to  pass  through  right-angled  prisms  P,  P. 

The  solid  black  lines  as  they  pass  from  the  two  points  to  the  eye 
indicate  the  uninterrupted  course  of  the  rays  as  they  would  pass 
without  the  prisms  and  show  the  relative  points  of  impression  on  the 
retina.  The  dotted  red  lines  show  the  diversion  of  the  course  of  these 
rays,  and  it  is  clear  that  the  course  of  the  rays,  &,  &,  from  B,  which 


152 


PHYSIOLOGY. 


under  ordinary  conditions  would  fall  at  the  temporal  side  from  the 
points  a,  a,  are  so  diverted  from  their  usual  course  that  they  will  fall 
at  &',  &',  or  at  the  nasal  side  of  the  retina  from  a,  a. 

Prof.  R.  W.  Wood1  has  suggested   a  more  convenient  form  of 


Fig.  55. — Wheatstone's  Pseudoscope. 

pseudoscope  which  can  be  arranged  hy  a  slight  modification  of  the 
ordinary  stereoscope.  A  pair  of  strong  convex  spherical  lenses  is  so 
placed  between  the  pictures  and  the  lenses  of  the  stereoscope  at 
suitable  distances  that  the  observer  sees,  not  the  pictures  directly,  but 
their  inverted  images. 


1  Science,  November,  1899. 


UNCONSCIOUS  CONCLUSIONS.  153 

SECTION  XVIII. 
UNCONSCIOUS  CONCLUSIONS.1 

Applying  the  principles  mentioned  in  the  last  section  to  experi- 
ments made  with  the  stereoscope,  we  are  able  to  explain  by  the  com- 
parisons which  may  be  made  between  these  experiments  and  our  ordi- 
nary experiences  many  of  the  phenomena  which  would  otherwise  re- 
main unexplained.  Then,  by  employing  these  results  we  may  reverse 
the  process  and  gain  a  clear  understanding  of  some  of  the  phenomena 
of  vision  which  have  only  been  understood  since  the  invention  of  the 
stereoscope. 

As  we  proceed  with  the  experiments  of  this  section  it  will  appear 
more  and  more  clear  that  the  acts  of  motion  of  the  eyes  are  the  basis 
upon  which  the  idea  of  space  as  recognized  by  the  visual  sense  is 
founded.  It  does  not  follow  that  motion  is  in  every  instance  of  judg- 
ment of  space  necessary,  but  that  the  experience  which  has  been  gained 
by  the  acts  of  motion  is  essential. 

The  experiment  of  Dove,  already  mentioned,  shows  that  an  ob- 
ject illuminated  by  an  electric  spark  may  be  located  in  space  although 
the  light  of  the  spark  has  not  continued  during  a  time  sufficient  to 
have  enabled  the  eyes  to  adjust  for  the  object.  Here  the  knowledge 
of  the  distance  and  direction  of  the  impression  made  upon  the  retina 
from  the  macula  permits  of  a  judgment  of  the  extent  and  direction 
of  the  movement  which  would  have  to  be  made  in  order  to  accomplish 
the  adjustment.  That  this  form  of  judgment  occurs  constantly  in 
respect  to  images  which  are  received  at  poiiits  outside  the  maculas, 
and  that  it  is  essential  to  binocular  perspective,  .was  long  since  shown 
by  Briick. 

While  it  is  true  that  the  visual  notion  of  space  is  the  result  of 
movements,  it  would  not  be  possible  to  execute  all  the  movements 
necessary  in  order  to  obtain  an  idea  of  the  outline  perspective  of  a 
complex  body  in  the  infinitely  brief  space  of  time  in  which  such  ideas 
are  usually  obtained.  Consciousness  is  not  the  result  of  a  single 
process. 

Thus  actual  movements  and  potential  efforts  combine  in  the  for- 
mation of  the  idea  of  visual  space. 

The  long  disputed  question  whether  the  ability  to  form  judgment 


1  This  section  on  "Unconscious  Conclusions"  is  the  substance  of  an 
address  given  before  the  Troy  Scientific  Association,  April  21,  1879,  in  which 
these  diagrams  were  used  with  stereoscopes  by  the  members. 


154  PHYSIOLOGY. 

from  the  signs  given  by  the  location  of  the  impressions  upon  parts  of 
the  retina  in  relation  to  the  macula  is  an  inherited  one,  as  the  "nativ- 
ists"  hold,  or  an  acquired  one,  as  the  "empyricists"  declare,  is  not 
essential  to  our  study.  It  may  not  be  out  of  place,  however,  to  ven- 
ture the  remark  that  it  is  most  probable  that  the  ability  is  derived 
both  from  inheritance  and  experience. 

The  ability  of  the  chick  to  aim  correctly  at  a  grain  of  meal  within 
the  first  hour  of  its  existence  has  long  been  a  stock  illustration  of  the 
nativists,  while  the  absolute  inability  of  the  young  child  to  judge  of 
visual  space  is  equally  the  argument  of  the  empyricist. 

The  question  which  might  arise  in  the  mind  of  one  not  wedded 
to  either  doctrine  is  whether  the  human  being,  the  highest  developed 
of  all,  has  inherited  less  from  his  ancestors  than  have  the  more  humble 
classes. 

Is  it  not  quite  possible  that  the  chick  enters  upon  life  with  the 
nervous  organization  nearly  perfect  in  all  the  essential  relations  of 
its  parts,  while  the  child  is  born  less  mature  in  this  respect? 

It  is  certain  that  some  of  the  faculties  in  the  human  subject  are 
developed  only  after  several  years  of  life.  It  is  possible  that  with  the 
growth  of  the  individual  there  is  not  only  the  accumulation  of  experi- 
ences but  a  development  of  the  inherited  faculties  which  become  im- 
mense factors  in  the  ability  to  construct  ideas  from  sensations. 

It  is  fortunate  that  of  the  various  channels  through  which  the 
mind  comes  in  contact  with  the  world,  that  through  which  it  acquires 
by  far  the  greatest  store  of  knowledge  is  the  one  with  whose  mechanism 
and  workings  we  are  best  informed. 

The  study  of  the  phenomena  of  vision  leads  us  to  the  belief  that 
our  acquaintance  with  our  surroundings  is  the  result  of  mental  de- 
ductions from  physical  signs.  The  impressions  received  by  the  visual 
sense  are  so  many  symbols  from  which  the  mind  draws  certain  con- 
clusions. 

This  method  of  drawing  conclusions  can  be  well  illustrated  by 
the  effect  upon  the  mind  caused  by  certain  combinations  of  diagrams, 
the  elements  of  which,  when  examined  under  ordinary  circumstances, 
appear  in  no  way  capable  of  presenting  the  appearances  which  they 
assume  under  circumstances  somewhat  modified. 

The  better  to  understand  the  significance  of  these  unexpected  ap- 
pearances we  should  bring  to  mind  the  more  generally  entertained  idea 
of  the  manner  in  which  objects  are  perceived  by  the  eye,  and  also  an 
important  but  less  generally  understood  view  of  the  p1ienomena.jA.c- 


UNCONSCIOUS  CONCLUSIONS.  155 

cording  to  the  more  popular  idea,  rays  of  light  from  the  different  parts 
of  an  object,  passing  into  the  eye  and  through  its  refractive  media, 
form  an  image  upon  the  retina,  or  at  least  cause  an  impression  of  an 
image,  which  impression  is  transmitted  from  the  retina,  where  it  is 
formed,  back  to  the  brain,  where  it  is  perceived.  This  idea  involves 
the  transmission  of  the  picture  or  impression  as  a  whole. 

The  other  idea  is  that  the  impression  caused  by  the  light  on  the 
retina  acts  as  a  sort  of  "finder,"  that  the  retina,  possessing  the  function 
of  recognizing  light  and  color,  acts  as  a  guide  to  muscles  which  move 
the  eyes,  and  that  the  movements  of  these  muscles  in  bringing  the  most 
sensitive  portion  of  the  retina  into  direct  relation  with  various  parts 
of  the  object  constitute  a  very  important  element  in  the  recognition  of 
the  form  and  position  of  the  object  seen.  In  other  words,  that  an  im- 
portant element  in  the  act  of  vision  is  the  mental  recognition  of  cer- 
tain muscular  contractions  by  means  of  which  the  eyes  are  adjusted. 
There  is  also,  in  the  conception  of  form,  distance,  and  depth,  the 
mental  comparison  of  the  two  images  or,  to  put  it  more  technically, 
the  two  sets  of  required  muscular  adaptations. 

It  will  be  seen  as  we  advance  that  these  latter  views  have  strong 
confirmation,  and  that,  so  far  as  they  are  correct,  they  indicate  that 
the  conception  of  an  object,  gained  through  the  sense  of  sight,  is  after 
all,  an  idea  made  up  from  a  variety  p^unconscip'us  conclusions. 

Beginning  with  ideas  of  a  simple  nature,  and  advancing  to  those 
more  complex,  we  may,  by  the  aid  of  a  few  diagrams  and  a  stereoscope, 
illustrate  the  manner  in  which  a  large  class  of  these  mental  conclusions 
are  reached. 

In  the  first  diagram  (Fig.  56)  are  two  series  of  rings,  arranged  at 
a  distance  suitable  for  the  stereoscope.  Each  series  is  like  the  other 
and  each  consists  of  several  rings  gradually  decreasing  in  diameter, 
each  smaller  being  included  in  the  next  larger.  The  rings  have  not  all 
a  common  center,  but  the  center  of  each,  as  it  becomes  smaller,  is  re- 
moved somewhat  nearer  toward  the  side  next  the  other  series  than  that 
of  the  next  larger,  until  we  reach  the  very  smallest,  which  is  exactly 
in  the  center  of  its  surrounding  ring. 

Looking  at  these  diagrams  with  the  stereoscope  we  see  the  two 
series  unite  as  one,  but  not  as  a  series  of  concentric  rings  on  a  flat 
surface.  The  rings  advance  toward  the  observer  from  the  larger  to 
the  smaller,  projecting  forward  like  a  cone  with  its  base  on  the  paper 
and  its  apex  in  the  air. 

If  we  can  give  a  reasonable  account  of  this  singular  and  beau- 


156 


PHYSIOLOGY. 


tiful  phenomenon  we  shall  have  at  the  same  time  made  a  step  in  com- 
prehending a  method  by  which  the  mind  arrives  at  a -conclusion  in 
respect  to  relative  distances. 

Let  us  then  examine  what  happens  as  we  look  through  the  glasses 
of  the  instrument.  These  glasses  are  essentially  prisms  with  their 
edges  set  toward  each  other.  The  effect  of  each  prism  is  to  bend  the 
light,  which  approaches  it  at  right  angles,  toward  its  base.  As  one 
looks  through  the  two  prisms  at  the  points  a  and  a  (Fig.  51)  the 
line  of  light  coming  from  a  is  bent  at  the  prism,  so  that  the  ob- 
server turns  the  eyes  in  the  direction  from  which  the  line  of  light 
from  each  image  appears  to  come.  As  the  eyes  are  thus  turned  to  meet 
the  line  of  light,  the  mental  effect  of  this  adjustment  is  to  locate  the 
image  a  at  a' ;  but  the  image  of  the  second  a  is  also  similarly  located, 


Fig.  50. 


so  that  the  two,  provided  that  each  consisted  of  a  single  element,  would 
unite  exactly  at  a'.  Here  we  encounter  a  difficulty,  for  the  figures  at  a 
and  a  are  not  simple  elements,  and  were  we  to  occupy  ourselves  with 
all  the  interesting  questions  which  might  arise  in  respect  to  this  illus- 
tration, we  would  be  slow  in  reaching  the  next  diagram  of  our  series. 
We  may  then  pass  directly  to  the  statement  that  in  this  case  the  im- 
aginary centers  of  the  two  largest  rings  would  meet  at  a'.  But  it  will 
be  observed  that  the  imaginary  centers  of  the  smallest  rings  are  not  so 
far  removed  from  each  other  as  the  larger.  As  the  prisms  will  bend 
the  line  of  light  from  the  smallest  as  much  as  the  largest,  it  follows 
that  the  imaginary  center  of  the  smaller  ring  at  a  will  be  thought  to  be 
a  little  beyond  a'  toward  b' ' ,  and  likewise  a  corresponding  excess  of 
displacement  of  the  smallest  ring  of  b.  In  order  to  form  a  mental  con- 


UNCONSCIOUS  CONCLUSIONS.  157 

ception  of  the  union  of  these  rings,  therefore,  they  must  be  supposed 
to  unite  at  a  point  at  which  lines  drawn  from  the  eyes  to  these  two 
points  would  cross;  that  is,  a  little  in  front  of  a'  at  a",  and  in  pro- 
portion as  the  muscular  contraction  for  the  convergence  of  the  two 
eyes  in  observing  the  different  pairs  of  rings  is  greater,  the  point  at 
which  the  lines  will  cross  is  nearer  to  the  observer.  Hence  the  ap- 
pearance of  a  series  of  rings  rising  toward  the  observer.  But  there  is 
still  an  interesting  point  to  be  observed.  Our  cone  is  not  perfect.  Its 
apex  is  cut  off,  and  in  the  center  of  the  section  is  a  dot  exactly  in  the 
plane  of  the  section.  Why  does  the  dot  not  advance  to  complete  the 
cone?  Because  each  of  the  dots  is  exactly  in  the  center  of  a  smaller 
ring,  and  the  convergence  of  the  eyes  for  the  combined  image  of  the 
dot  is  exactly  the  same  as  the  average  convergence,  or  the  convergence 
for  the  imaginary  centers  of  the  rings.  This  experiment  illustrates 
well  the  effect  of  the  muscular  adjustments  upon  our  ideas  of  relative 
distance. 

It  may  be  said :  "This  is  an  interesting  optical  illusion !''"  But 
it  is  in  reality  a  mental  conclusion  formed  in  the  manner  in  which 
such  conclusions  are  commonly  formed.  Then  in  what  respect  does 
it  differ  from  the  conclusions  formed  under  ordinary  circumstances? 
In  this :  that  the  result  does  not  conform  to  the  result  of  the  impres- 
sion gained  by  another  important  sense.  If  we  pass  our  finger  along 
the  surface  on  which  the  diagram  is  printed  we  find  that  it  encounters 
no  raised  cone  of  rings,  it  passes  over  a  perfectly  flat  surface.  In  ordi- 
nary life  the  two  senses  agree.  The  infant  sitting  upon  a  smooth  floor 
passes  its  hand  along  its  surface  and  finds  that  he  neither  raises  nor 
depresses  the  hand.  The  eyes  follow  the  hand  and  he  is  conscious  of 
no  relative  change  in  the  angle  at  which  the  two  are  directed. 

Suddenly  the  hand  encounters  a  wooden  cone  and  follows  it  to 
its  summit.  As  the  muscles  of  the  arm  elevate  the  hand,  the  muscles 
of  the  eyes  perform  a  corresponding  convergence.  Thus  the  two  classes 
of  simultaneous  movements  are  occupied  with  the  same  object.  And, 
day  by  day  and  year  by  year  these  two  senses,  touch  and  sight,  cor- 
rect and  supplement  each  other.  This  does  not  indicate  that  the  infant 
is  entirely  destitute  of  that  innate  consciousness  of  relation,  position, 
and  distance  which  enables  the  just-hatched  chick  to  seize  its  prey.  It 
is  enough  to  say  that  in  the  child  the  idea  of  position  as  recognized 
by  sight  is  largely  learned  from  muscular  adjustments  of  the  eyes, 
which  correlate  with  adjustments  of  the  muscles  which  are  governed 
by  the  sense  of  touch.  Whether,  as  Wundt  holds,  the  visual  sense 


PHYSIOLOGY. 


precedes  the  tactile,  is  not  the  question.  It  is,  however,  certain  that 
the  two  senses  supplement  each  other  in  the  formation  of  the  ideas 
of  extension  and  of  depth. 

If  now  we  have  gained  an  idea  of  how  we  may  arrive  at  a  con- 
ception of  nearness  and  distance  we  may  advance  to  a  more  complicated 
class  of  conclusions.  And  here,  even  more  than  in  the  first  instance, 
we  shall  see  that  what  appears  to  us  as  a  simple  impression  of  sight 
is  in  reality  the  result  of  a  process  of  abstract  reasoning.  (Fig.  57.) 

As  we  examine  this  second  diagram  without  the  aid  of  the  stere- 
oscope we  see  each  figure  made  up  of  two  discs  of  exactly  equal  diam- 


Fig.  57. 

eter  separated  by  lateral  lines,  and  that  the  centers  of  one  pair  of 
discs  are  nearer  to  each  other  than  the  other.  Using  the  stereoscope 
we  now  obtain  a  most  interesting  result.  The  two  pairs  of  discs  are 
united,  the  combined  image  of  one  pair  in  advance  of  the  other.  To 
this  phenomenon  we  can  apply  the  lesson  already  learned.  But  here  is 
a  new  and  interesting  principle.  The  most  distant  disc  is  much  larger 
than  the  other.  Examine  the  diagrams  again  without  the  prisms. 
All  the  discs  are  of  a  like  diameter.  How  then  does  one  appear  larger 
than  the  other?  If  a  disc  of  a  certain  size  were  to  be  placed  a  foot 
in  front  of  an  eye,  the  eye,  in  looking  along  any  diameter  of  the  disc, 
would  move  through  a  certain  angle.  If  another  disc  were  placed 
exactly  behind  the  first  at  a  distance  of  two  feet,  it  would  require  to 


UNCONSCIOUS  CONCLUSIONS.  159 

be  much  larger  in  order  that,  the  eye  moving  through  the  same  angle, 
that  is,  moved  by  an  equivalent  muscular  adjustment,  should  see  each 
border.  We  may  therefore  say,  if  the  eye  must  move  through  equal 
angles  in  passing  along  the  diameters  of  two  discs  at  unequal  dis- 
tances, that  the  one  which  is  furthest  removed  from  the  eye  will  be 
the  largest. 

Eeturning  to  our  diagram,  we  have  reached  the  conclusion  that 
one  of  these  discs  is  in  advance  of  the  other.  But  as  the  eye  moves 
to  an  equal  extent  from  side  to  side  of  each  disc  we  reason  that  of 
necessity  the  disc  farther  removed  must  be  the  larger.  Look  as  long 
as  we  please,  we  cannot  reverse  this  judgment.  Here  then  we  have 
reached  a  primary  conclusion,  and  then,  basing  our  opinion  upon 
the  conclusion  already  formed,  we  draw  a  second  conclusion,  namely, 
that  whereas  one  of  these  discs  is  nearer  to  us  than  the  other,  and 
whereas  the  eye  must  make  as  great  an  excursion  in  passing  from  one 
side  to  the  other  of  the  most  distant  as  of  the  nearest  disc,  therefore 
the  former  is  greater  than  the  latter. 

Here  it  will  be  in  order  once  more  to  recur  to  the  inquiry  whether 
in  reality  the  eye  must  move  so  as  to  bring  the  most  sensitive  point 
of  the  retina  in  linear  relation  to  the  different  points  of  an  object 
in  order  to  estimate  its  size,  and,  again,  whether  in  order  to  see  the 
object  singly  with  both  eyes  the  image  must  fall  upon  this  sensitive 
point  of  both  eyes,  or  indeed  of  any  corresponding  points  of  the 
retina  of  both  eyes.  The  experiment  known  to  physiologists  in  which 
a  person  looking  into  a  perfectly  dark  box  sees  an  electric  spark  as  a 
single  impression,  or  by  the  illumination  of  this  spark  unites  stereo- 
scopic diagrams,  shows  that  under  certain  circumstances  retinal 
sensations  may  be  felt  at  points  not  exactly  corresponding,  yet  be 
received  by  the  mind  as  a  single  impression.  For,  in  looking  into 
such  a  dark  box,  the  eyes  cannot  be  supposed  to  be  adjusted  so  that 
the  visual  line  of  each  would  be  directed  to  the  point  at  which  the 
spark  would  occur,  nor  adjusted  for  the  haploscopic  diagrams,  and 
the  duration  of  the  spark  is  too  brief  to  permit  time  for  any  such 
adjustment.  Hence,  at  least  under  such  circumstances,  the  mind 
accepts  an  impression  under  conditions  in  which  the  principle  of 
muscular  adjustments,  upon  which  we  have  based  the  explanation  of 
the  results  of  the  experiments  just  made,  does  not  appear  absolutely 
to  prevail.  Even  these  exceptions  are  not,  however,  opposed  to  the 
more  common  experience,  for  when  such  sensations  fall  upon  non- 
corresponding  points  the  mind  may  at  once  draw  an  inference  from 


160 


PHYSIOLOGY. 


the  amount  of  adjustment  which  may  be  required  to  bring  the  sen- 
sations upon  corresponding  points,  that  is,  the  potential  movement. 

A  running  horse  estimates  the  force  which  must  be  expended 
in  leaping  the  ditch  in  front  of  him  before  the  leap  is  made.  In  a 
similar  way  the  amount  of  energy  required  for  adjustment  of  the 
eyes  is  estimated  before  the  adjustment  is  made. 

Passing  now  to  a  class  of  phenomena  in  which  the  principle  of 
mental  conclusion  from  muscular  adjustment,  as  already  illustrated, 
is  somewhat  differently  applied,  we  examine  the  third  stereoscopic 
diagram.  (Fig.  58.)  Without  the  aid  of  the  instrument  we  notice 
a  pair  of  rectilinear  figures,  the  outer  lines  of  which  are  exactly  alike. 
Within  the  outer  frame-work  in  each  figure  three  sides  of  a  parallelo- 


Fig.  58. 


gram,  in  heavy  lines,  join  the  right  side  of  the  framework,  which 
completes  the  parallelogram.  Here  for  the  first  time  the  figures  are 
not  symmetrical,  the  heavy  lines  extending  further  across  the  right 
hand  frame  than  the  left. 

Employing  the  instrument,  another  interesting  phenomenon  is 
observed.  The  framework  is  perfectly  united  at  once,  and  after  a 
moment  the  heavy  lines  also,  but  these  latter  swing  backward  like 
an  open  door.  By  what  process  of  reasoning  can  these  two  figures 
induce  this  conception? 

The  following  diagram  may  assist  us  in  understanding  the  phe- 
nomenon (Fig.  59)  : — 

Suppose  the  eyes  at  A  and  B  are  directed  toward  c  d,  which  may 
represent  the  space  of  a  door,  ce  representing  the  door  swung  open. 


UNCONSCIOUS  CONCLUSIONS. 


161 


In  looking  at  the  door  space  the  eye  A  moves  through  the  angle  cAd, 
or  from  c  to  d.  The  eye  at  B  makes  an  exactly  equal  excursion. 
Directing  the  gaze  at  the  door  itself,  however,  it  will  he  seen  that  the 
eye  at  A  will  make  a  smaller  excursion,  that  is,  from  c  to  e' ,  and  the 
eye  at  B  would  also  make  an  excursion  less  than  cd,  but  greater  than 
ce'  (from  d'  to  c),  but  that  every  excursion,  both  for  the  space  and 
the  door,  reaches  the  point  c.  In  other  words,  in  looking  at  an  open 
door  arranged  as  in  this  figure  the  eyes  make  equal  excursions  for  the 
open  space  and  shorter  but  unequal  excursions  for  the  swinging  door. 
These  are  the  elements  in  the  stereoscopic  figure,  and  because  these 
elements  conform  to  the  ordinary  experience  in  adjusting  the  eyes  the 


Fig.  59. 

mind  arrives  at  the  conclusion  that  the  object  seen  does  not  differ 
from  what  would,  under  ordinary  circumstances,  induce  the  corre- 
sponding ocular  movements. 

The  same  principle  carried  further  will  give  other  effects,  such 
for  instance  as  is  seen  in  the  diagram  representing  the  guide-post. 
Here  we  get  the  principle  of  the  door  opening  toward  us  and  opening 
from  us.  (Fig.  60.) 

Not  only  are  the  movements  of  the  eyes  made  instrumental  in 
the  mental  estimation  of  the  physical  characteristics  of  an  object 
examined,  but  many  of  our  ideas  gained  from  the  appearances  of 
objects  are  gained  through  a  process  of  conclusions  in  which  the 
sense  of  touch  would  appear  to  have  instructed  the  sense  of  sight. 
Although  this  brings  us  in  some  sense  beyond  the  limit  of  muscular 
action,  the  general  subject  of  these  unconscious  conclusions  is  so  re- 
markably well  illustrated  by  an  examination  of  the  elements  which 
enter  into  our  idea  of  luster  that  it  may  be  profitably  considered  in 


162 


PHYSIOLOGY. 


this  relation.  Examining  with  the  stereoscope  the  diagram  in  which 
one  parallelogram  is  white,  the  other  black,  a  tilted  mirror  is  seen. 
The  principles  already  considered  give  the  reasons  for  this  tilting. 
The  question  of  special  interest  here  is  how  to  account  for  the  un- 
expected result  of  the  stereoscopic  combination  of  a  black  and  a  white 
surface.  Ordinarily  a  mingling  of  black  and  white  does  not  produce 
luster.  We  should  expect  it  to  produce  either  black  or  gray,  and  two 
dull  surfaces  are  not  supposed  to  unite  to  make  a  lustrous  one.  Let 
us  take  in  our  hand  an  object  which  gives  a  lustrous  appearance — a 
perfectly  smooth-cased  gold  watch,  a  smooth  silver  cup,  or  any  such 
article  which  gives  the  effect  of  luster.  Passing  the  hand  over  it 


II 


II 


I  TO  _  N.Y 


BOSTON! 


Fig.  60. 

we  find  two  prominent  characteristics;  first,  the  surface  is  composed- 
of  elements  closely  combined,  giving  a  greater  or  less  degree  of 
density,  and  in  the  second  place,  the  particles  constituting  this  dense 
surface  are  exactly  in  the  same  plane.  That  is,  the  different  super- 
ficial particles  are  never  raised  in  irregular  order,  one  above  another. 
As  we  pass  the  hand  we  experience  the  sense  of  smoothness.  What 
effect  will  this  perfect  smoothness  of  the  surface  produce  upon  light? 
First,  the  diffused  light  will  pass  to  the  eye  as  it  would  from  a  ball 
of  wool  or  from  a  rough  pebble;  but  second,  another  phenomenon 
will  result  which  would  not  result  in  the  case  of  the  ball  of  wool 
or  the  rough  pebble.  As  the  direct  light  from  some  strongly  illu- 
minated point  in  the  surrounding  space  falls  upon  this  surface  of 
dense  and  evenly  disposed  particles  it  is  strongly  reflected.  If  the 


UNCONSCIOUS  CONCLUSIONS. 


163 


surface  is  curved  these  reflected  rays  light  up  certain  portions  of  the 
surface  much  more  strongly  than  others.  Surfaces  of  which  the 
superficial  particles  are  roughly  adjusted  with  respect  to  each  other 
do  not  ordinarily  give  off  these  reflected  rays. 

Here  then  are  two  classes  of  sensations  combined  so  nearly  uni- 
versally as  to  become  firmly  associated  as  characteristics  of  a  certain 
class  of  conditions.  There  is  the  sense  of  density  and  of  perfect  uni- 
formity of  surface,  gained  from  the  touch ;  then  there  is  the  sense 
of  the  impression  made  by  the  diffused  light  in  the  eye  and  also  the 
effect  of  the  strong  reflected  rays.  When  the  hand  feels  a  surface 
of  this  kind  in  the  dark  the  idea  of  the  two  kinds  of  light  enters  the 
mind,  and  when  we  see  an  object  giving  off  from  the  same  surface 
a  weaker  and  a  much  stronger  light  the  mind  at  once  associates  the 


Fig.  61. 


phenomenon  with  that  of  a  perfectly  smooth  surface.  Here  then 
we  have  the  associated  ideas  of  luster.  Looking  now  at  our  stereo- 
scopic figure  we  have  the  usual  elements  of  luster  as  they  are  pre- 
sented to  the  eye,  a  weak  light  coming  from  the  dark  surface  and  a 
much  stronger  light  coming  from  the  white  one.  The  mind  at  once 
enters  upon  a  process  of  inference  from  which  it  quickly  evolves  the 
idea  of  the  lustrous  mirror  surface. 

Thus,  returning  to  the  experiments  in  form  and  distance,  without 
entering  upon  any  discussion  of  the  relative  merits  of  the  question 
whether  the  mind  derives  its  conceptions  of  the  appearances  of  visible 
objects  directly  from  the  impression  made  upon  the  retina,  or  more 
indirectly  through  a  wonderful  series  of  muscular  adjustments  by 
which  corresponding  portions  of  the  two  retinae  are  brought  into 
direct  relations  with  the  various  parts  of  the  object,  we  are  able  to 
see  that  beyond  all  question  these  delicate  and  intricate  muscular 


164  PHYSIOLOGY. 

actions  which  guide  the  eyes  are  notably  calculated  to  serve  as  media 
through  which  ideas  of  space  and  form  may  be  obtained. 

It  is  easy  to  see  that  many  evils  might  result  from  imperfections 
in  the  instrumentalities  through  which  these  remarkable  adjustments 
must  be  made,  and  we  may  find  important  subjects  for  reflection  in 
the  nicety  of  the  machinery  and  the  necessity  of  all  its  parts  working 
without  needless  friction. 

Directing  our  thoughts  to  the  side  of  the  relations  of  the  prin- 
ciples already  illustrated  to  conceptions  of  the  beautiful  in  art,  we 
find  that  the  character  of  the  movements  of  the  eyes  as  governed  by 
the  various  muscles  which  direct  their  visual  axes  is  that  which  largely 
contributes  to  the  kind  and  degree  of  pleasure  derived  from  the  con- 
templation of  an  artistic  design. 

It  would  be  difficult  or  impossible  for  us  to  conceive  how  a, 
picture  with  regular  yet  varied  curves  formed  at  the  retina  and  trans- 
mitted to  the  brain,  should  cause  a  more  soothing  effect  upon  the 
mind  than  one  with  jagged  and  irregular  outline.  If,  on  the  other 
hand,  we  think  of  the  muscles  of  the  eyes  directing  them  along  the 
undulations  of  soft  curves  or  following  around  rough  and  ragged  out- 
lines, we  can  see  that  in  one  case  there  will  be  pleasurable  but  easy 
movement,  while  in  the  other  there  will  be  uneven  or  jerky  move- 
ments, which  may  be  tiresome  or  only  stimulating,  depending  on 
their  nature.  On  the  theory,  then,  that  the  pleasure  gained  in  look- 
ing at  a  picture  or  building,  at  a  book  or  at  the  gestures  of  a  speaker, 
depend  upon  movements  of  the  eyes  in  following  the  outlines  of 
stationary  objects  or  the  movements  of  the  active  objects,  it  will  be 
seen  that  in  order  to  induce  continuous  pleasure  these  movements 
must  be  varied.  There  must  be  easy  swinging,  monotonous  drifting, 
sudden  changes,  and  even  irregular  and  harsh  movements.  The  pic- 
ture which  would  excite  various  emotions  must  combine  these  various 
classes  of  lines. 


SECTION  XIX. 

THE  FIELD  OF  BINOCULAR  VISION. 

In  the  ordinar}?-  vision  with  two  eyes  there  is  a  part  of  the  field 
in  which  objects  are  seen  by  both,  for  a  part  of  the  field  seen  by  one 
eye  extends  over  a  part  of  the  field  seen  by  the  other.  There  is  also 
a  part  of  the  visual  field  of  each  eye  which  is  seen  only  by  itself. 


THE  FIELD  OF  BINOCULAR   VISION. 


165 


This  may  be  shown  by  the  simple  experiment  of  observing  the  extent 
of  the  visual  field  while  both  eyes  are  used  and  then  slipping  a  card 
in  front  of  one  eye  when  some  of  the  objects  which  were  in  the  com- 
mon field  will  be  no  longer  visible.  Or  if  one  brings  the  right  hand 
from  behind  forward  until  it  just  enters  the  field  and  then  closes  the 
right  eye  the  hand  will  no  longer  be  within  the  visual  field.  By  ad- 
vancing the  hand  it  again  enters  the  space  in  which  objects  are  seen. 
By  experiments  of  this  kind  but  more  carefully  ordered,  the  extent 


Fig.  62. — The  Common  Field  of  Vision. 

of  the  field  which  is  common  to  the  two  eyes  and  that  which  belongs 
to  each  eye  separately  may  be  ascertained. 

The  conformation  of  the  face,  especially  the  prominence  of  the 
nose  and  of  the  brows,  is  an  important  factor  in  the  common  field  of 
vision. 

The  approximate  area  of  the  common  and  of  the  individual 
fields  when  the  eyes  are  directed  to  a  fixed  point  is  indicated  in  the 


166  PHYSIOLOGY. 

accompanying  diagram.  That  part  of  the  diagram  (Fig.  62)  en- 
closed by  the  outer  strong  red  lines  suggests  the  whole  field  of  view. 
That  part  which  is  not  shaded  is  the  portion  common  to  both  eyes, 
while  of  the  shaded  portions,  that  to  the  right  of  the  line  indicated 
by  90°  belongs  to  the  right  eye  only  and  that  to  the  left  of  that  line  is 
seen  only  by  the  left  eye. 

Since  it  is  only  within  a  limited  part  of  the  field  of  view  that 
objects  are  seen  simultaneously  by  both  eyes,  it  is  only  within  a 
limited  part  of  the  field  of  view  that  the  true  sense  of  depth  or  the 
perspective  of  the  third  dimension  is  perceived.  Within  that  field, 
impressions  of  sight  derived  from  surrounding  objects  are  received 
upon  the  two  retinas,  but  owing  to  the  varied  positions  of  such  objects 
within  the  field  of  sight  these  impressions  cannot  all,  nor  indeed  a 
considerable  proportion  of  them,  be  received  simultaneously  on  cor- 
responding portions  of  the  retinas. 

Unless,  therefore,  there  were  some  system  of  selection  of  im- 
pressions which  the  mind  should  choose  to  recognize  there  must  result 
a  chaos  of  confused  sensations  from  which  no  just  idea  of  the  objects 
seen  could  be  formed  in  the  consciousness. 

As  a  matter  of  fact  the  eyes  can  make  such  selections,  and  it  is 
possible,  by  appropriate  movements,  to  place  the  two  eyes  in  such 
relations  to  each  other  that  a  certain  selected  part  from  the  general 
aggregation  of  sensations  recognized  by  the  eyes  shall  fall  upon  the 
parts  of  the  retinas  which  are  so  related  to  each  other  in  the  mind 
that  they  may  be  said  to  be  coinciding  or  corresponding  points. 


SECTION  XX. 
OF  CORRESPONDING  POINTS. 

Johannes  Mtiller,1  employing  a  method  which  had  been  intro- 
duced twenty  years  before  by  Purkinje,2  of  inducing  subjective  images 
from  both  retinas  by  scleral  compression,  arrived  at  the  conclusion 
that,  in  general,  corresponding  points  of  the  two  retinas  are  those 
which,  were  the  two  latter  overlying  so  that  the  poles,  with  the  vertical 
and  horizontal  meridians,  would  be  in  contact,  all  other  identical 
points  would  be  corresponding  points.  Later  researches  by  Hering, 


1Handbuch  d.  Physiologic,  1838. 

2  Beobachtungen  iiber  Versuche  zur  Phy.siolog.  d.  Sinne,  2,  44f.,  1819. 


CORRESPONDING  POINTS.  167 

Helmholtz,  Yolkmann,  Van  Moll,  and  Bonders,  introduced  the  doc- 
trine which  appeared  to  be  universally  established  until  the  intro- 
duction of  the  clinoscope,  that,  while  the  doctrine  of  Miiller  would 
apply  to  horizontal  meridians  it  would  not  apply  to  the  vertical 
meridians  of  the  retinas,  since  these  last  were  supposed  to  diverge 
above  and  the  divergence,  by  common  consent,  was  equal  to  about 
1*4°  for  each  retina;  though  Bonders,  Van  Moll,  and  others  thought 
that  the  divergence  above  might  be  considerably  greater.  The  early 
results  of  examinations  by  the  clinoscope  demonstrated  that  in  all 
cases  in  which  the  vertical  meridians  lean  the  horizontal  meridians 
lean  in  a  corresponding  direction  and  to  an  equal  extent. 

.  Corresponding  points  of  the  two  retinas  are,  by  no  means,  with 
a  single  exception,  anatomically  symmetrical  points.  There  is  no 
evidence  in  support  of  the  old  view  that  a  nerve  filament,  in  its 
course  between  its  origin  in  the  brain  and  its  place  in  the  retina, 
divides  so  that  one  part  may  be  supplied  to  each  retina.  Except  the 
condition  of  hemianopia  there  is  no  evidence  of  anatomical  sym- 
metry. With  the  existing  knowledge  of  the  subject  we  have  only  to 
recognize  the  phenomena. 

Recognizing  that,  with  the  exception  of  the  maculas,  we  are 
unable  to  locate  corresponding  points  by  anatomical  symmetry,  phil- 
osophers have,  as  we  have  seen  above,  with  what  has  appeared  a 
plausible  degree  of  precision,  located  them  from  their  geometrical 
relations.  These  observers  apparently,  in  the  search  for  the  purely 
physical  explanation  of  corresponding  points,  forgot  that  binocular 
vision  is  something  more  than  a  mere  series  of  physical  phenomena 
such  as  might  occur  in  a  passive  optical  instrument. 

It  is  desirable  that  the  doctrine  should  be  considered  from  this 
purely  physical  side  in  order  that  we  may  discover  the  inadequacy 
of  the  reasoning  and  that  we  may  be  better  prepared  to  consider  the 
somewhat  more  difficult,  but  the  more  satisfactory,  doctrine  of  a  com- 
bination of  physical  and  psychical  phenomena. 

Stating  the  doctrine  as  it  has  been  accepted  and  as  it  is  now 
accepted  in  works  of  physiological  optics,  it  may  be  expressed  as  fol- 
lows : — 

If  the  image  of  a  given  point  is  located  at  the  temporal  side  of 
the  macula  of  the  right  eye  the  impression  will  also  be  located  at  the 
nasal  side  of  the  macula  of  the  left  eye  and  at  a  distance  from  it  equal 
to  that  of  the  impression  of  the  right  eye  from  the  macula.  Also,  if 
the  image  is  impressed  at  a  horizon  above  that  which  passes  through 


168 


PHYSIOLOGY. 


the  masculas  or  below  that  horizon,  the  impression  for  each  eye  will 
be  equally  above  or  below  this  horizon. 

These  points  are  not  anatomically  but  geometrically  similar. 
A  glance  at  Fig.  63  will  make  the  principle  of  the  doctrine  plain. 

Let  A  and  B  be  the  two  retinas  and  X  and  X'  the  two  maculas. 
If  the  selected  impression  is  located  on  the  retina  A  at  0  (i.e.,  at  the 
temporal  side  of  the  macula)  it  will  be  located  at  the  point  0'  of  the 
retina  B  at  the  nasal  side  of  the  macula  and  at  the  same  distance 
from  X'  as  0  is  from  X. 

It  at  once  appears  that  the  two  retinal  points  0  and  0'  are,  from 
an  anatomical  point,  in  widely  different  localities. 

But  these  two  points  will  not  only  be  equally  removed  from  the 
maculas,  they  will  be  on  corresponding  horizontal  meridians  of  the 


-X 

O' 


Fig.  63. — Maculas  and  Corresponding  Points  According  to  the 
Accepted  Doctrine. 

two  retinas.  Thus  if  the  point  0  is  on  the  horizontal  meridian  pass- 
ing through  the  macula  at  X,  the  point  0'  will  be  on  the  horizontal 
meridian  passing  through  the  macula  at  X'.  Also  if  the  point  0'  is 
situated  on  a  horizontal  meridian  above  or  below  the  meridian  of  X 
the  point  0  will  be  on  a  horizontal  meridian  equally  above  or  below 
the  meridian  of  X ''. 

Helmholtz  thus  states  the  law  of  corresponding  points : — 
"Upon   the  apparently  vertical   concordant   lines1    (of  the  two 
eyes),  points  which  are  at  equal  distances  from  the  horizontal  meri- 
dians are  corresponding  points."     And  "points  which  in  the  retinal 


1  Helmholtz  here  speaks  of  "apparently  vertical  lines,"  referring  to  his 
view  that  the  vertical  meridians  are  not  truly  vertical  while  the  horizontal 
lines  are  truly  horizontal. 


CORRESPONDING  POINTS.  169 

horizons  are  at  equal  distances  from  the  point  of  fixation  are  corre- 
sponding points/'1 

In  respect  to  corresponding  points  in  the  field  of  vision  we  may 
again  quote :  "Corresponding  points  in  the  two  visual  fields  are  those 
which  are  at  equal  distances  and  equal  in  direction  from  the  corre- 
sponding horizontal  and  apparently  vertical  meridians."- 

While  this  proposition  is  not  altogether  clear,  it  is  evident,  from 
the  context,  that,  according  to  it,  a  series  of  points  equally  distant 
in  the  field  of  view  and  from  which  proceed  lines  of  direction  toward 
points  of  the  retina  equally  distant  from  the  maculas  and  in  corre- 
sponding meridians,  are  corresponding  points. 

The  proposition  first  quoted  and  this  last  cannot  both  be  true 
except  under  circumstances  entirely  at  variance  with  Helmholtz's 
illustrative  experiments.  These  experiments  are  made,  not  with 
curved  surfaces,  hollow  spheres,  but  with  plane  surfaces  like  the 
usual  stereoscopic  cards  or  the  pages  of  a  book. 

The  propositions  of  Helmholtz  are  inconsistent  with  his  exam- 
ples. Indeed  points  of  the  two  retinas  which  are  at  one  moment 
corresponding  points  may  at  the  next  moment  be  non-correspondent 
if  the  ocular  adjustments  have  changed.  If  we  accept  the  experi- 
ments of  Yolkmann,  which  are  quoted  and  endorsed  by  Helmholtz, 
it  must  follow  that  the  accepted  theory  is  not  tenable.  The  following 
is  one  of  Tolkmann's  experiments  which  Helmholtz  characterizes  as 
"exact."  While  accepting  this  characterization  it  must  also  be  con- 
ceded that  it  is  by  no  means  conclusive.  Indeed,  it  falls  far  short 
of  a  demonstration  of  the  proposition  he  is  aiming  to  prove. 

"A  rectangular  cross  is  formed  before  each  eye  by  the  horizontal 
a,  a'  (Fig.  64)  and  the  verticals  s  and  s',  the  distance  between  which 
should  be  equal  to  the  interval  of  the  eyes  of  the  observer.  Below 
the  horizontal  line  and  at  the  external  side  of  each  vertical  there  are 
traced  two  other  horizontals  b  and  V  of  which  the  one,  b,  is  fixed, 
while  the  other,  &',  is  mobile  parallel  to  itself.  The  observer  fixes  the 
centers  of  the  two  crosses  in  such  a  manner  as  to  obtain  fusion.  Then 
the  mobile  horizontal,  b',  is  adjusted  in  such  a  way  that  it  becomes, 
apparently,  a  prolongation  of  &,  which  is  immovable  in  the  other 
visual  field." 


•"Optique  Physiolog.,"  p.  880  and  886. 
Ibid,  p.  896." 


170 


PHYSIOLOGY. 


The  distance  from  the  eyes  was  300  millimeters.  When  the  mov- 
able horizontal  was  adjusted  so  as  to  appear  precisely  as  a  prolonga- 
tion of  the  fixed  horizontal,  it  was  found,  as  the  result  of  many  ex- 
periments, that  the  distance  of  the  two  horizontals  from  the  main 
horizontal  line  was  always  the  same.  Many  experiments  can  be  made 
which  will  more  effectually  prove  that  on  a  plane  surface  equally 
removed  points  will  be  recognized  as  such  by  both  eyes  acting  simul- 
taneously. Such  experiments  I  have  made  in  various  ways  by  many 
devices  and  they  all  indicate  that  in  the  field  of  regard  points  of 
equal  distance  and  in  corresponding  directions  from  the  point  of 
fixation  and  in  a  plane  at  right  angles  to  the  plane  of  regard  when 
that  plane  is  in  the  horizontal  direction  and  the  head  is  in  the  pri- 


a- 
b- 


•a' 


Fig.  64. — Volkmann's  Diagram. 

mary  position,  fall  upon  corresponding  points  of  the  two  retinas. 
This  does  not  indicate  that  the  corresponding  points  for  equal  dis- 
tances in  the  plane  are,  in  the  vault  of  the  retina,  at  equal  distances 
from  each  other.  Quite  the  contrary,  these  corresponding  points 
must  be  variable,  the  variation  depending  upon  the  differential  values 
of  the  angles  formed  by  the  direct  line  of  sight  and  a  line  connecting 
another  given  point  with  the  retina.  Let  us  suppose  the  point  of 
fixation  to  be  removed  15  inches  in  front  of  the  eyes,  rather  further 
than  in  Volkmann's  experiment,  and  in  the  median  and  horizontal 
plane.  (Fig.  65.)  Suppose  also  that  the  points  A,  B,  C,  etc.,  be  at 
intervals  of  one  centimeter  each.  These  distances  being  equal,  the 
distances  of  the  points  of  the  retinas  at  which  the  impressions  would 
be  received  will  be  unequal.  For  each  of  the  angles  ARE,  BEG,  etc., 


CORRESPONDING  POINTS.  171 

arc   unequal.      Moreover,   the   increments   to   consecutive   angles   are 
unequal,  as  it  is  plain  from  the  text  beneath  the  figure. 

One  of  the  conclusive  proofs  that  retinal  corresponding  points 
are  not  at  geometrically  equal  distances  in  the  two  retinas  is  that  a 


Fig.  65. — Let  R  and  L  be  the  nodal  points  of  the  two  eyes  and  A  the 
point  of  fixation.  The  points  B,  C,  etc.,  are  outside  the  point  of  fixa- 
tion. Suppose 

RO  —  1.25  in.,  OA  =  15  in. 

</MO  =  4°  45'  49" 

(  <ARB  =  l°  53'  26"       (  <ARC  =  3°  46'  1" 
I  <ALB  =  l°  54'  5"         I  <ALC  =  ^°  39'  58". 

The  points  corresponding  to  the  incidence  of  the  lines  CR  and  CL  are  not 
thus  equally  removed  from  the  maculas. 


172  PHYSIOLOGY. 

straight  line  drawn  in  the  vertical  or  in  the  horizontal  direction  does 
not  appear  curved  as  it  would  positively  do  were  the  accepted  doctrine 
correct.  Hence  the  accepted  view  that  the  points  of  retinal  corre- 
spondence are,  by  superficial  measurement,  equal,  is  incorrect.  The 
ratios  of  consecutive  pairs  of  increments  cannot  be  simply  stated,  but 
may  be  determined  by  the  method  shown  above. 

Nevertheless  there  is  a  mental  cognizance  of  relations  of  dis- 
tances in  space  and  distances  on  the  retinal  surfaces.  They  are  recog- 
nitions of  angular  values  rather  than  of  equally  removed  spatial 
values  on  the  retinas.  In  the  section  on  the  "Horopter"  this  view  will 
be  more  fully  developed. 

Xew  elements  enter  the  problem  when  the  eyes  are  in  conver- 
gence with  depression  or  elevation.  In  the  case  of  depression  the  ver- 
tical meridians,  by  the  act  of  adjustment,  are  caused  to  lean  with  the 
upper  part  of  the  meridian  toward  the  temporal  side  and  the  lower 
part  toward  the  median  side.  Hence,  the  lower  parts  of  the  meri- 
dians approach  each  other  and  the  upper  parts  recede.  Xow,  since 
a  point  in  the  lower  portion  of  the  field  of  regard  is  connected  with 
the  upper  part  of  the  retina  by  a  straight  line  passing  from  one  to 
the  other,  and  since  a  straight  line  connects  a  point  in  the  upper 
part  of  the  field  of  regard  with  the  lower  part  of  the  retina,  it  follows 
that  if  a  point  in  space  in  the  lower  part  of  the  field  of  regard  is  to 
be  received  at  corresponding  points  of  the  two  retinas,  the  lines  lead- 
ing from  the  point  to  the  retinas  will  spread  at  a  greater  angle  than 
will  the  lines  connecting  a  point  in  space  in  the  upper  part  of  the 
field  of  regard.  This  lessening  of  the  angle  for  the  upper  part  of 
the  field  of  regard  and  the  increase  of  the  angle  for  the  lower  part 
of  the  field  would  throw  the  upper  part  of  the  field  of  regard  for- 
ward and  draw  the  lower  part  backward,  so  that  the  plane  of  the 
field  of  regard  would  no  longer  be  at  right  angles  to  the  plane  of 
regard,  but  would  form  with  it  an  obtuse  angle,  which  would  increase 
in  proportion  to  the  convergence  and  depression.  An  opposite  result 
would  follow  convergence  with  elevation  of  the  plane  of  regard. 

This  very  important  principle  becomes  an  element  of  the  greatest 
moment  in  the  investigation  of  the  subject  of  the  horopter. 

Should  the  two  eyes  be  directed  to  a  given  point  so  that  the  image 
of  the  point  would  fall  at  the  two  maculas  it  is  evident  that  a  certain 
number  of  other  points  in  the  common  field  of  view  would  fall  upon 
non-corresponding  points.  For  example,  should  one  look  at  a  table, 
all  of  the  legs  and  all  of  the  angles  could  not  fall  upon  corresponding 


CORRESPONDING  POINTS.  173 

points  simultaneously.  The  mind  may  not  choose  to  take  cognizance 
of  any  doubling  of  the  images  from  these  non-corresponding  points. 
In  the  ordinary  course  of  the  use  of  the  eyes  no  notice  is  taken  of 
such  phenomena.  Just  as  one  who  is  absorbed  in  listening  to  an 
eloquent  address  within  a  hall  may  not  be  conscious  of  the  sounds 
of  a  brass  band  playing  outside,  although,  if  attention  were  to  be 
directed  to  them,  the  sounds  of  the  instruments  might  be  distinct, 
so  in  the  visual  field  impressions  not  directly  conducive  to  the  object 
of  sight  may  be  neglected  or  they  may  become  indirectly  important 
accessories  to  vision. 

A  very  simple  experiment  will  assist  in  making  clear  the  state- 
ment that  in  the  field  of  binocular  view  the  greater  number  of  objects 
are  not  seen  singly. 

If  with  one  hand  the  person  making  the  experiment  holds  a 
pencil  at  the  distance  of  one  foot  directly  in  the  median  line  in  front 
of  the  eyes,  it  will  appear  as  a  single  pencil.  But  if  he  holds  with 
the  other  hand  another  pencil,  in  the  same  line  and  at  two  feet  dis- 
tance, the  first  pencil  will  appear  double  as  soon  as  the  gaze  is  directed 
beyond  it  to  the  second  pencil.  (Fig.  66.) 

If  the  position  of  the  double  images  of  the  first  pencil  is  exam- 
ined it  will  be  seen  that  they  are  crossed,  but  if  the  gaze  is  again 
changed  to  fix  the  first  pencil  the  second  will  appear  double  and  the 
images  will  be  homonymous. 

Eepeating  the  experiments  in  various  ways  it  will  be  seen  that 
if  the  eyes  are  fixed  upon  a  point  at  a  given  distance  all  nearer  objects 
in  the  same  line  and  in  many  other  lines,  will  seem,  when  the  con- 
sciousness is  directed  to  the  phenomenon,  doubled  heteronymously, 
and  more  remote  objects  will  appear  doubled  homonymously. 

The  diagram  (Fig.  66)  illustrates  the  position  of  the  images  of 
the  more  remote  object  when  the  lines  of  sight  of  the  two  eyes  are 
fixed  upon  the  near  object.  If  the  impression  from  the  near  object 
M  falls  upon  the  macula  at  ra  and  ra',  then  the  impression  of  the 
image  of  the  object  N  will  fall  to  the  inner  (nasal)  side  of  the 
macula.  Referring  to  page  167  it  will  be  seen  that  the  impressions 
thus  caused  cannot  be  united  to  form  a  single  image.  The  two 
images  will  appear,  each  on  the  same  side  as  the  eye  that  receives  it 
and  at  an  angle  with  the  line  of  vision  directed  to  the  near  object, 
equal  to  the  angle  mon  formed  by  the  crossing  of  the  lines  as  they 
pass  through  the  nodal  point.  This  would  bring  the  images  of  the 
distant  object  at  PP',  in  the  plane  with  the  object  M,  at  right  angles 


174 


PHYSIOLOGY. 


to  the  median  plane.  This  is  the  theoretical  position  of  these  images. 
But  there  enters  here  another  principle,  a  purely  psychological  one, 
which  will  be  discussed  in  another  section,  by  which  the  images  are 
projected  to  the  distance  of  the  plane  of  the  real  object  N.  The  images 


then  appear  at  the  distance  of  PM  and  P'M  removed  in  the  lateral 
direction,  and  at  the  actual  distance  of  MN  beyond  the  near  object. 
When  it  is  considered  that  in  almost  every  field  of  binocular  sight 
there  are  many  objects  and  at  various  distances,  it  will  appear,  as 
has  been  already  stated,  that  but  a  comparatively  small  number  of 


CORRESPONDING  POINTS.  175 

these  objects,  or  these  points  in  space,  can  fall  upon  corresponding 
points  of  the  two  retinas. 

Are  the  images  of  these  points  or  objects  which  are  seen  doubly 
mentally  suppressed  ?  Does  the  mind  shut  them  out,  refusing  to  take 
cognizance  of  them,  or  do  they  actually  constitute  an  important,  if 
not  an  essential,  part  of  the  physical  impressions  which  unite  to  con- 
stitute the  basis  for  a  complete  mental  conception  of  the  field  of 
view  ? 

Undoubtedly  the  latter  contingency  is  the  correct  one,  as  will 
be  more  fully  shown  in  the  succeeding  section. 

We  may  for  illustration  of  this  introduce  the  experiences  derived 
through  another  sense.  The  melody  of  tones  is  not  derived  simply 
from  the  uniform  vibrations  required  to  form  sounds  of  certain  pitch. 
We  have,  for  example,  the  sound  of  the  human  voice  repeated  by  the 
phonograph  or  the  graphophone.  The  principal  vibrations,  the 
stronger,  are  repeated  by  the  instrument.  But  the  voice  has  lost  its 
melody.  The  sounds  of  the  machine  are  caricatures  of  the  tones  of 
the  voice,  without  sweetness  or  melody,  because  the  instrument  fails 
to  repeat  the  lesser  vibrations,  the  under  and  over  tones,  which  are 
characteristic  in  the  voice  itself. 

So  would  it  be  could  a  method  be  devised  by  which  only  the  parts 
of  the  field  of  vision  in  which  images  are  received  upon  spatially  cor- 
responding points  of  the  retinas  would  be  recognized.  The  beauty 
of  perspective  and  of  the  harmony  of  objects  in  the  field  of  view 
would  be  absent,  although  the  skeleton  of  the  field  of  regard  might 
remain.  Experience  of  some  persons  subject  to  gradual  atrophy  of 
the  optic  nerve  illustrates  the  principle,  for  when  the  field  of  view 
is  much  reduced  they  are  unable  to  see  their  way  to  walk,  though 
they  may  read  letters  directly  in  front  of  them  at  the  standard  dis- 
tances. 

The  images  which  fall  upon  spatially  non-corresponding  points 
therefore  serve  an  essential  purpose.  They  serve  as  finders  in  the 
field  of  space.  By  means  of  these  peripheral  images  not  only  are  the 
eyes  enabled  to  turn  from  one  object  to  another  and  from  one  part 
of  the  same  object  to  another  part,  but  there  is  a  mental  estimate  of 
their  relative  positions  on  the  retinas,  from  which  conclusions  respect- 
ing the  positions  of  objects  in  space  are  drawn.  These  processes, 
except  for  the  presence  of  these  images  which  some  writers  have  sup- 
posed are  mentally  suppressed,  could  be  effected  by  a  series  of  trials 
and  even  then  could  be  effected  most  imperfectly. 


176  PHYSIOLOGY. 

What  has  been  said  of  single  images  when  the  impressions  are 
located  at  corresponding  points,  and  of  double  images  when  they 
are  located  at  non-corresponding  points,  is  then,  in  an  important 
sense,  a  physical  law,  but,  as  it  has  been  shown,  there  are  circum- 
stances which  indicate  that  a  higher  law  governs  all  these  phenomena. 
It  is  the  law  of  unconscious  conclusions.  Perhaps  the  psychologist 
might  express  the  psychic  process  by  some  other  term,  but  the  term 
which  I  have  used  appears  to  me  to  express  the  actual  process  with 
sufficient  accuracy. 

If  a  person  has  a  slight  paresis  of  one  of  the  superior  recti 
muscles  he  may  be  able  to  bring  the  images  to  what  would  appear 
to  be  corresponding  points,  for  there  is  neither  lateral  nor  vertical 
displacement,  yet  the  image  seen  by  the  affected  eye  appears  beyond 
the  other.  It  is  customary  to  elevate  the  line  of  regard  when  looking 
at  distant  objects  and  to  depress  it  for  near  objects.  Since  the  effort 
to  raise  the  affected  eye  to  the  given  plane  of  vision  is  greater  than 
for  the  other  and  greater  than  the  life  experience  of  the  affected  per- 
son has  found  necessary,  its  image  is  assigned  to  a  more  distant  point. 

Many  examples  might  be  cited  to  show  that  the  purely  spatial 
view  of  corresponding  points  is  insufficient  to  explain  all  the  phe- 
nomena. 

Yet  none  of  these  examples  furnish  evidence  that  the  mind  shuts 
out  any  part  of  the  impression  made  upon  the  retina,  but  all  appear 
to  me  to  point  to  a  mental  process  which,  taking  cognizance  of  all 
the  physical  sensations,  arranges  them  in  logical  relation  to  each 
other  with  a  rapidity  which  is  incomprehensible. 

If  the  diagrams  in  the  section  on  "Unconscious  Conclusions"  are 
examined  with  the  aid  of  the  stereoscope  it  will  be  seen  that  in  each 
instance  parts  of  the  diagrams  which  by  the  law  of  Helmholtz  could 
not  be  regarded  as  corresponding  points  in  the  visual  field,  are  united 
as  corresponding  points  in  the  mental  conception  of  the  form  of  the 
object. 

Helmholtz  himself  introduces  diagrams1  to  illustrate  this  prin- 
ciple, to  which  attention  had  been  called  by  Wheatstone,  the  inventor 
of  the  stereoscope. 

We  may  then  sum  up  our  conclusions  respecting  this  subject  in 
the  following  statement: — 

Corresponding  points  are  those  points  in  the  retinas  ivhich  an- 


1  "Optique  Physiologique,"  p.  960. 


THE  HOROPTER.  177 

swer  to  proportional  degrees  of  rotations  of  the  eyes  about  their  cen- 
ters of  rotation,  and  which,  from  given  points  in  Hie  plane  of  the 
point  of  fixation,  receive  incident  rays  ivhich  must  pass  through  the 
nodal  points. 

They  represent  therefore  the  relation  between  the  muscular  and 
the  retinal  senses. 


SECTION  XXI. 

THE  HOROPTER.1 

Of  all  the  subjects  in  physiological  optics  none  has  been  thrown 
into  greater  confusion  by  conflicting  views  of  different  investigators 
and  none  has  been  surrounded  by  greater  mystery  than  that  of  the 
horopter.  Helmholtz,  after  devoting  about  ninety  pages  of  his  monu- 
mental work  on  physiological  optics  to  the  horopter,  pages  replete 
with  experiments  and  with  abstruse  mathematical  formula?,  evolved  a 
theory  which  no  other  investigator  could  verify,  even  of  the  few  who 
claimed  to  be  able  to  understand  it.  With  all  this  erudite  labor  and 
with  all  the  enthusiastic  interest  of  the  great  philosopher  he  worked 
out  a  single  horopter  of  the  infinite  number  which  may  exist,  and 
even  that  one,  being  based  on  false  premises,  was  absolutely  faulty 
for  well-adjusted  eyes  and  entirely  impracticable  for  any  eyes. 

It  is,  therefore,  when  all  the  divergent  opinions  are  considered, 
not  altogether  without  an  appearance  of  justice,  that  so  astute  a  man 
as  Giraud-Teulon  should  have  characterized  the  horopter  as  a  "trans- 
cendental fancy." 

"When,"  he  says,  "all  the  labor  of  determining  the  surface  curve 
(fulfilling  the  geodesical  condition  of  the  horopter)  was  ended,  it 
was  discovered  that  this  surface  assumed  the  form  of  a  torus.  .  .  . 
It  was  not  noticed  that  a  table  with  four  legs,  a  chair  placed  before 


lThis  section  was  read  before  the  New  York  Branch  of  the  American 
Psychological  Association  and  the  Section  of  Anthropology  and  Psychology 
of  the  New  York  Academy  of  Sciences,  at  Yale  University,  New  Haven, 
October  20,  1903,  and  was  printed  in  the  Psychological  Review,  May,  1904.  A 
few  slight  modifications  and  additions,  taken  from  a  paper  read  before  the 
American  Medical  Association,  in  May,  1904,  are  here  introduced,  while  some 
portions  have  been  transferred  to  the  section  on  "Corresponding  Points"  and 
another  section. 

12 


178  PHYSIOLOGY. 

us,  were  seen  singly,  although  they  certainly  had  none  of  the  attrib- 
utes of  a  torus."1 

Nevertheless  the  subject  of  the  horopter  or,  to  put  it  better,  of 
horopters,  is  one  of  great  practical  importance.  We  may  emphasize 
the  expression  and  say  that  it  is  one  of  preeminent  importance. 

A  horopter  may  be  defined  as  consisting  collectively  of  all  the 
points  in  space  whose  images,  ivith  a  given  adjustment  of  the  eyes, 
fall  upon  corresponding  points  of  the  two  retinas. 

Notwithstanding  the  view  I  have  expressed  of  the  notable  rank 
which  should  be  accorded  to  this  subject,  the  general  definition,  as 
just  given,  is  almost  the  only  point  concerning  the  phenomena  of 
horopters  on  which  investigators,  those  who  have  conceded  a  horopter, 
have  agreed. 

By  some  it  has  been  described  as  a  line,  by  others  as  a  surface, 
and  by  Helmholtz,  especially,  as  a  most  complex  and  quite  incom- 
prehensible combination  of  curves,  planes,  and  straight  lines. 

Without  entering  upon  the  merits  of  Helmholtz's  propositions 
that  the  horopter  is  "a  line  of  double  curvature  produced  by  the  in- 
tersection of  surfaces  of  the  second  degree  (hyperboloid  to  a  nappe, 
cone,  or  cylinder),"  that  "it  is  a  straight  line  and  a  curved  plane  of 
the  second  degree,"  etc.,  we  may  for  a  moment,  without  accepting  the 
doctrine,  consider  the  position  of  the  horopter  according  to  this  phil- 
osopher when  the  plane  of  regard  is  directed  to  the  horizon. 

"In  a  single  case  only,"  says  Helmholtz,  "is  the  horopter  a  sur- 
face, it  is  when  the  point  of  regard  is  situated  in  the  horizontal  and 
median  planes  and  at  infinite  distance.  The  plane  of  the  horopter  is 
then  parallel  to  the  plane  of  regard.  ...  In  the  case  of  normal 
eyes  thus  directed  toward  the  horizon  the  horopter  coincides  approxi- 
mately with  the  ground  on  which  the  observer  walks." 

If  we  consider  this  proposition  with  care  it  will  appear  that  if 
it  were  correct  its  accuracy  would  involve  much  ocular  inconvenience. 
We  do  not  look  at  the  horizon  when  we  walk.  One  who  would  hold 
the  head  erect  and  direct  the  eyes  to  the  horizon  would  stumble  often 
in  his  march.  But,  according  to  the  proposition,  if  the  eyes  should 
be  directed  to  the  ground  at  a  few  feet  in  advance  of  the  pedestrian 
he  would  bury  his  horopter  beneath  the  soil,  and  all  the  objects  in 
his  pathway  would  appear,  so  far  as  a  horopter  is  concerned,  con- 
fused and  indistinct. 


1  "The  Function  of  Vision."     Translated  by  Owen. 


THE  HOROPTER. 


179 


I  have  taken  so  much  space  with  an  introduction  in  order  that 
we  may  at  the  outset  form  an  idea  of  the  present  state  of  the  doctrine. 
Kecurring  to  our  definition,  if  a  horopter  is  the  collection  of  the 
points  in  space  whose  images,  with  a  given  adjustment  of  the  eyes, 
fall  upon  corresponding  points  of  the  two  retinas,  it  follows  that 
horopters  succeed  each  other  in  endless  variety  and  with  amazing 
rapidity.  With  every  glance  of  the  eyes,  with  the  passing  of  the  line 
of  regard  from  one  part  of  the  page  of  a  book  to  another,  in  fact,  with 
every  change  of  the  head,  of  the  body,  or  of  the  eyes  themselves  and 
with  every  degree  of  convergence  a  new  horopter  is  developed.  A 
horopter  will  be  formed  when  the  two  eyes  are  so  adjusted  as  to 


Fig.  67. — Helmholtz's  Figure  Indicating  the  Position  of  the  Horopter 
when  the  Eyes  are  directed  toward  the  Horizon.  A,  The  Direction  of 
the  line  of  regard.  DE,  The  Horopter. 


enable  the  image  of  the  point  fixed  to  be  located  exactly  at  the 
maculas  of  the  two  retinas. 

The  innate  impulsion  to  form  a  practically  complete  horopter 
with  any  given  fixation  is  so  imperious  that  only  insurmountable 
obstacles  will  serve  as  a  restraint. 

Two  tenets  or  conceptions  constitute  the  essential  foundation  for 
the  doctrine  of  the  horopter.  They  are,  the  theory  of  the  position 
and  direction  of  the  meridians  of  the  retinas  and  the  theory  of  corre- 
sponding points. 

In  respect  to  both  tenets  Helmholtz  and  most  modern  searchers 


180  PHYSIOLOGY. 

in  this  field  have  adopted  views  which  have  resulted  in  the  confusion 
in  which  the  subject  has  been  involved.  Before  we  can  proceed  to 
the  phenomena  of  the  horopter,  then,  it  is  essential  to  obtain  a  cor- 
rect idea  of  these  two  fundamental  theories. 

We  speak  of  vertical  and  of  horizontal  meridians  of  the  retina. 
They  are,  like  the  meridians  of  the  globe,  imaginary  lines,  yet  they 
have  distinct  relation  to  sight  impressions.  For  example,  let  us  sup- 
pose a  horizontal  meridian  passing  through  the  macula,  the  eye  being 
directed  straight  forward  and  the  head  being  in  the  primary  position. 
The  eye  fixes  a  given  point,  the  image  of  which  is  impressed  at  the 
macula.  Now  if  another  point  at  one  side  of  this  point  of  fixation 
is  situated  on  a  higher  plane  than  the  point  of  fixation,  its  image 
will  be  impressed  at  one  side  of  the  macula  and  below  the  horizontal 
meridian.  It  is  unnecessary  to  consider  in  detail  this  doctrine,  as  we 
may  assume  an  understanding  of  the  general  principles  as  they  have 
been  stated  in  the  preceding  section.  Helmholtz,  Volkmann,  Hering, 
and  other  investigators  came  to  the  more  or  less  uniform  conclusion 
that  the  horizontal  meridians  were  all  parallel  with  the  external 
horizon,  but  that  the  vertical  meridians  were  only  apparently  vertical, 
and  that  they  leaned  out  above  and  approached  each  other  below. 
Helmholtz's  experiments  led  him  to  the  belief  that  the  vertical  meri- 
dians of  each  eye  leaned  out  about  1  1/4°-  A  number  of  investigators 
immediately  found  that  their  vertical  meridians  in  each  and  every 
instance  leaned  out  exactly  1 14°. 

My  own  researches  led  me  to  devise  the  clinoscope,  which  has 
become  a  most  important  and  essential  instrument  in  practical  exami- 
nations of  the  eyes.  One  of  the  first  things  which  the  clinoscope  did 
was  to  demonstrate  that  these  leanings  are  natural  defects — personal 
peculiarities — and  that  they  vary  with  different  individuals  from  one 
to  many  degrees;  that  the  vertical  meridian  is  at  a  right  angle  with 
the  horizontal  and  that  it  is  rare  to  find  two  persons  in  succession  who 
record  the  same  leaning.  These  leanings  I  have  called  declinations. 

Abundant  experience  in  the  correction  of  these  defects  of  de- 
clination have  demonstrated  beyond  all  reasonable  doubt  that  the 
proper  position  for  a  vertical  meridian  is  the  vertical  position. 

That  Helmholtz  had  what  I  have  called  a  plus  declination  for 
each  eye  I  am  convinced.  There  is  much  reason,  however,  to  believe 
that  it  was  considerably  in  excess  of  iy±°. 

Thus,  Helmholtz  included  in  his  most  elaborate  mathematical 


THE  HOROPTER.  181 

calculations  his  individual  defects,  which  he  assumed  were  physio- 
logical features  common  to  mankind. 

This  was  one  of  the  fundamental  errors. 

The  second  foundation  tenet  is  the  doctrine  of  corresponding 
points  of  the  retina. 

The  question  of  corresponding  points  has  already  been  discussed 
in  the  preceding  section,  and  it  is  only  necessary  here  to  recall  our 
new  definition  of  corresponding  points  as  those  points  in  the  retinas 
which  answer  to  proportional  degrees  of  rotations  of  the  eyes  about 
their  centers  of  rotation,  and  which,  from  given  points  in  the  plane 
of  the  point  of  fixation,  receive  incident  rays  which  must  pass  through 
the  nodal  points.  They  represent  therefore  the  relation  betwen  the 
muscular  and  the  retinal  senses. 

This  definition,  while  less  easy  to  comprehend  than  it  is  to  divide 
the  retinas  into  squares  of  millimeters  and  point  off  so  many  to  the 
temporal  side  of  one  and  so  many  to  the  medial  side  of  the  other 
retina  and  call  these  corresponding  points,  has  the  advantage  of  being 
in  harmony  with  the  phenomena  of  vision. 

As  we  have  seen,  the  actual  movements  of  the  eyes  about  the 
rotation  centers  are  not  always  essential  to  an  estimation  of  the  rela- 
tive positions  of  objects  in  space.  In  the  absence  of  the  objective 
movement  there  is  the  subjective  conception  of  the  impulse  required 
to  induce  a  given  movement.  Recurring  to  the  experiment  of  Dove, 
when  the  box  is  illuminated  by  the  electric  spark  the  image  at  the 
further  end  is  seen  singly,  although,  considering  the  position  which 
the  eyes  would  naturally  have  assumed,  there  should  be  double  images. 

In  such  a  case,  the  consciousness  of  a  single  image  for  each 
retina  and  of  its  position  external  to  the  macula  leads  to  the  con- 
clusion that  a  convergence  of  the  eyes  would  be  required  to  locate 
the  image  at  the  macula,  and  the  extent  of  the  required  motion  would 
indicate  the  angle  of  convergence  and,  therefore,  the  distance  of  the 
spark.  Of  course,  there  are  other  elements  in  this  complex  psychical 
phenomenon,  but  that  mentioned  is  enough  to  suggest  the  course  of 
the  psychical  process.  It  is  such  processes  of  unconscious  conclusions 
that  bring  many  points  within  the  field  of  vision  into  a  subjective 
horopter. 

The  subjective  horopter  is  of  the  utmost  importance  and  is  gov- 
erned by  fixed  laws.  The  physical  horopter,  including  the  points  in 
space  actually  impressed  at  corresponding  points  of  the  two  retinas, 
may  be  regarded  as  the  skeleton,  while  the  subjective  horopter,  includ- 


182  PHYSIOLOGY. 

ing  points  in  space  which  are  impressed  at  such  points  on  the  retinas 
as  correspond  to  a  demand  for  certain  exact  movements  of  the  eyes 
necessary  in  order  to  place  the  image  at  the  macula  of  each  eye,  con- 
stitute a  mental  assemblage  of  the  lineaments  of  harmonic  visual 
impressions.  We  may  renew  the  comparison  of  this  subjective  hor- 
opter  to  the  overtones  of  a  musical  sound.  The  fundamental  tone 
is  not  pleasing ;  it  is  noise ;  it  is  the  skeleton  of  the  tone.  But  when 
combined  with  its  multiplicity  of  overtones,  which  even  the  ear  of 
the  expert  musician  fails  to  differentiate,  the  musical  tone  finds  its 
body  and  affords  pleasure  to  the  listener. 

In  the  subjective  horopter  the  consciousness  of  the  required 
movements  takes  the  place  of  the  actual  movements,  as  it  does  in  the 
Dove  experiment. 

This  doctrine  of  a  subjective  horopter  does  not  by  any  means 
provide  for  a  confused  jumble  of  space  perceptions,  either  in  the 
retinas  or  in  the  mind.  Every  object  in  the  subjective  horopter  is  as 
much  subject  to  the  laws  of  -angular  valuation  of  muscular  movements 
as  are  the  objects  in  the  physical  horopter.  We  are  to  keep  in  mind 
the  principle  that  while  the  image  of  a  given  point  in  space  may  fall 
on  physically  non-corresponding  points  of  the  retinas,  a  sub-liminal 
consciousness  determines  the  relative  positions  of  these  two  non- 
corresponding  points  to  the  macula  of  the  two  eyes,  and  concludes 
on  the  impulse  which  would  be  demanded  to  make  an  actual  adjust- 
ment for  the  macula  were  such  movements  to  be  executed;  and  it  is 
this  unconscious  conclusion,  based  on  accurate  data,  that  places  the 
object,  singly,  in  its  appropriate  position  in  the  field  of  view  and  at  the 
proper  distance  relative  to  other  objects  in  that  field. 

In  our  horopter,  objects  less  distant  than  the  point  of  fixation 
may  still  be  within  this  subjective  horopter,  their  images  being 
impressed  on  the  two  retinas  at  points  corresponding  for  the  lines  of 
incidence  on  one  or  other  side  of  the  macula.  Then  they  will  appear, 
as  in  the  experiment  of  Dove,  single.  The  principles  controlling 
psychic  phenomena  in  that  experiment  are,  in  this  case,  modified  to 
meet  the  different  conditions.  Thus,  a  great  number  of  objects 
within  a  fairly  wide  range  may  be  brought  within  a  perfect  horopter. 

If  the  direction  of  the  gaze  is  changed  while  the  head  remains 
in  the  primary  position  a  new  horopter  must  be  and  is  formed. 

When  the  point  of  fixation  is  at  infinite  distance  and  in  the 
median  plane,  all  horizontal  meridians  are  horizontal  and  all  vertical 
meridians  are  vertical.  So  also  if  in  the  plane  of  the  horizon  the 


THE  HOROPTER.  183 

point  of  fixation  is  brought  nearer,  the  meridians  maintain  their 
original  relations,  and  these  relations  will  also  continue  if  the  eyes  are 
directed  upward  or  downward,  provided  the  visual  lines  remain  paral- 
lel. But  if  the  point  of  fixation  is  at  such  distance  as  to  demand  con- 
vergence of  the  lines  of  regard,  and  if  it  is  above  or  below  the  horizon 
(the  head  being  supposed  to  be  in  the  primary  position),  all  hori- 
zontal and  all  vertical  lines  assume  new  directions.  The  eyes  rotate 
on  their  antero-posterior  axes.  This  form  of  rotation  is,  as  we  have 
seen,  known  as  torsion.  These  torsional  rotations  are  governed  by 
fixed  laws,  and  the  general  principle  is  known  as  the  law  of  Listing. 

Should  the  visual  lines  of  the  two  eyes  converge  at  the  same 
time  that  the  plane  of  regard  is  depressed  the  horizontal  meridians 
of  each  eye  will  tilt  downward  toward  the  temporal  side  and  upward 
toward  the  medial  side.  The  vertical  meridians  will  also  tilt  with 
the  upper  part  outward  and  the  lower  part  inward.  The  tilting  is 
in  every  case  in  proportion  to  the  depression  and  the  lateral  direction 
of  the  line  of  vision. 

Accepting  the  two  basic  principles  as  they  have  been  stated,  and 
with  an  understanding  of  the  laws  of  torsion,  we  are  in  position  to 
examine  the  phenomena  of  the  horopter,  eliminating  the  mathematical 
intricacies  of  Helmholtz  and  substituting  only  simple  calculations  in 
plane  trigonometry.  It  will  not  be  necessary  to  inquire  in  detail 
into  its  form  in  many  positions;  three  will  suffice  to  illustrate  the 
principles,  and  the  details  of  only  one  of  these  need  be  given. 

First,  the  observer  directs  the  gaze  toward  the  horizon  in  the 
median  plane  at  infinite  distance,  the  head  being  in  the  primary  posi- 
tion. A  horopter  is  formed  at  the  distance  of  the  point  of  fixation 
and  it  will  be  a  plane  surface  at  right  angles  to  the  plane  of  regard. 
Objects  within  or  beyond  the  distance  of  the  point  of  fixation  will 
not  be  in  the  objective  horopter,  but  may  be  in  what  we  have  termed 
a  subjective  horopter.  They  may  be  impressed  on  the  two  retinas  and 
they  will  appear,  as  in  the  case  of  the  spark  or  the  figure  in  the  Dove 
experiment,  as  single,  the  principles  control-ing  the  psychical  phe- 
nomena in  that  experiment  being  here  modified  to  meet  these  different 
conditions. 

Second,  if  the  gaze  is  directed  somewhat  downward  and  to  a 
point  a  few  feet  in  advance,  as  in  the  case  of  a  person  walking,,  the 
horopter  will  still  be  very  nearly  at  right  angles  to  the  plane  of  regard, 
tipping  forward  slightly,  since,  although  there  is  depression  (a  nega- 
tive ascensional  angle)  of  the  plane  of  regard,  the  convergence  (the 


184  PHYSIOLOGY. 

lateral  angle)  is  so  slight  as  to  induce  small  torsional  action  and  the 
principle  of  ohjective  and  subjective  horopter  may  he  applied  as  in 
the  first  case. 

There  is,  also,  at  the  lower  part  of  the  field  of  view  a  bending 
in  of  the  horopter,  so  that  more  of  the  pathway  is  in  the  horopter 
than  would  he  were  it  through  its  whole  extent  a  plane. 

Coming  to  the  third  case  we  may  proceed  in  more  mathematical 
detail. 

i          Let  us  suppose  the  case  in  which  the  eyes  are  directed  to  the 
page  of  a  book  in  the. ordinary  position  for  reading. 

Assume  that  the  gaze  is  directed  so  that  the  point  of  fixation  is 
in  the  median  plane,  and  that  the  plane  of  regard  is  depressed  35°. 
Assume  also  that  the  distance  between  the  nodal  points  of  the  two 
eyes  is  21/o  inches  and  that  the  convergence  of  the  eyes  (the  lateral 
angle)  is  for  each  eye  5°.  We  have  from  these  data  to  determine 
the  distance  of  the  horopter  and  its  form  and  position  relative  to  the 
plane  of  regard. 

To  determine  the  distance  of  the  point  of  fixation  (which  will 
be  in  the  center  of  the  horopteric  field)  we  have  the  base,  2^2 
inches,  and  the  lateral  angles,  5°.  Taking  one  half  the  base  and 
one  lateral  angle  we  have  a  base  of  114  inches,  a  right  angle  and 
an  angle  of  5°  to  find  the  perpendicular  or  distance  from  the  base 
line  to  the  page  of  the  book  which  is  readily  found  to  be  14.287 
inches.  (Fig.  68.) 

The  distance  being  ascertained  by  the  formula  %  =  cot  A,  a 
being  the  base,  1.25  inches,  A  the  angle  opposite  the  base  and  &  the 
distance  sought.  At  this  distance  from  the  base  line  the  image  of 
the  point  of  fixation  will  be  exactly  at  the  macula  of  each  eye. 

According  to  the  law  of  torsions  by  this  depression-  of  the  gaze 
and  the  convergence  the  meridians  will  have  left  the  horizontal  and 
vertical  positions.  Referring  to  the  table  of  torsions  found  in  Helm- 
holtz's  work1  we  find  that  for  the  ascensional  angle  of  35°  and  lateral 
angle  of  5°  the  tilting  of  the  horizontal  (and  of  the  vertical)  meri- 
dians is  1°  35'.  These  conditions  being  given,  what  will  be  the  rela- 
tion of  a  straight  line  passing  horizontally  through  the  point  of  fixa- 
tion across  the  page  to  the  horizontal  meridians  of  the  retinas  now 
tilted  1°  35'  from  the  actual  horizon?  A  series  of  points  in  a  straight 


1  "Optique  Physiologique,"  p.  607. 


THE  HOROPTER.  -   185 

line  thus  passing  through  the  point  of  fixation  must  impress  them- 
selves along  the  horizontal  meridian  of  each  eye,  otherwise  the  points 
will  appear  confused  or  double.  But  how  can  this  series  of  points  in 
a  horizontal  line  he  impressed  upon  the  meridians  which  are  tilted  up 
toward  the  nasal  side  each  1°  35'? 

It  is  a  most  interesting  fact  that  the  images  of  these  points  will 
in  fact  be  thus  impressed  exactly  along  these  tilted  meridians  of  the 
retina,  and  it  is  precisely  because  these  meridians  of  the  retina  are 
thus  tilted  that  it  is  possible  for  the  impressions  to  be  made  along 
the  proper  meridians. 

Too  much  space  would  be  occupied  were  we  to  enter  upon  a 
mathematical  demonstration  of  this  statement,  but  a  little  considera- 
tion by  one  familiar  with  the  relation  of  lines  and  angles  will  show 
that  in  principle  the  statement  is  correct.  A  demonstration  however 


Fig.  68.— Angle  A  =  5°,          -  =  Cot  A,         ft  =  14.287. 


would  show  that  beyond  a  certain  degree  (10°  to  20°)  in  the  plane 
of  regard  a  straight  line  actually  appears  to  curve. 

We  come  next  to  the  more  complicated  question  in  respect  to 
the  position  of  a  line  running  from  the  top  to  the  bottom  of  the  page. 
Will  this  line  be  at  right  angles  to  the  plane  of  regard  as  the  hori- 
zontal one  is  parallel  with  it  or  will  it  lean  more  or  less  toward  or 
from  the  plane  of  regard? 

We  may  select  points  above  and  below  the  point  of  fixation  and 
determine  their  distance  from  the  base  line,  and  thus  obtain  the  angle 
of  the  surface  of  the  book  to  the  plane  of  regard. 

Take,  first,  a  point  5°  above  and  one  5°  below  the  point  of 
fixation.  The  distance  of  the  point  of  fixation  from  the  base  line 
connecting  the  nodal  points  has  already  been  determined  at  14.28  -f- 
inches.  In  that  case  there  was  a  lateral  angle  of  5°  for  each  eye. 
Now,  since  the  vertical  meridian  of  the  retina  tilts  out  as  it  rises 


186  PHYSIOLOGY. 

above  the  macula  this  lateral  angle  will  increase  as  the  image  is  im- 
pressed above  the  macula  and  it  will  decrease  in  proportion  to  the 
extent  that  the  impression  is  made  below  the  macula.  Before  we 
can  proceed,  therefore,  it  is  necessary  to  find  the  exact  amount  of 
increase  and  decrease  for  the  selected  points  5°  above  and  5°  below 
the  point  of  fixation,  since  our  angle  of  convergence  will  increase  in 
proportion  to  the  extent  to  which  the  vertical  meridian  leans  out 
from  its  original  position  exactly  at  the  selected  distance  and  decrease 
in  proportion  as  the  meridian  leans  in  below  the  macula  at  the  selected 
distance. 


Fig.  69.— Angle  A  =  l°  35',  "  =;Tan  A,        Tan  A  =  .02764, 

ft  =  5,         a  =  5  X. 02765        =0°  8'  52y3". 


We  may  find  the  extent  of  removal  by  the  formula : — 

I  =  tan  A  ;  tan  A  —  .02764, 

a  =  5  X  .02764  =  0.1382°  =  8'52i/2"  (Fig.  69). 

In  which  &  is  the  selected  distance  above  or  below  the  macula,  a  the 
required  increase  (or  decrease)  in  the  lateral  angle  and  A  the  angle 
of  1°35'. 

This  gives  .1382  of  a  degree  which  is  to  be  added  to  our  lateral 
angle  (angle  of  convergence),  when  we  can  proceed  as  in  the  first 
case  to  find  the  distance  from  the  base  line  to  the  selected  point 
below  the  point  of  fixation  (Fig.  70),  |  =  cot  A,  in  which  &  is  the 
distance  sought,  a  the  base  line,  1.25  inches,  A  the  angle  opposite  a, 
5°. 138.  From  this  we  find  that  &  =  13.904  inches. 

To  obtain  the  distance  of  the  point  above  the  point  of  fixation 


THE  HOROPTER. 


187 


we  must  subtract  the  0°.138  (0°  8'  52i/2")  from  5°,  when  by  the  same 
formula  we  find  the  distance  to  be  14.6976  inches  (Fig.  71.) 
We  have  now  the  distances 

5°  above  the  point  of  fixation 14.6976 

At  the  point  of  fixation 14.287 

5°  below  the  point  of  fixation 13.905 

Forming  from  these  distances  two  triangles  by  joining  the  three 
lines  at  their  extremities  we  have  a  line  joining  them  and  forming 


Fig.  70.— Angle  A  =  5°  8'  52ya". 

bases  which  represent  a  vertical  line  in  the  horopter  at  the  level  of 
the  page  of  the  book.     (Fig.  72.) 

The  acute  angle  at  this  surface  of  the  book  for  the  upper  tri- 
angle of  these  two  is,  69°  38'.  That  of  the  lower  triangle  is  70° 
48'  50". 


Fig.  71.— Angle  A  =  4°  51'  7y2". 

We  have  thus,  in  the  space  of  10°  up  and  down  the  page,  a  curve 
of  about  1°.  In  other  words,  the  horopter  in  this  direction  is  approx- 
imately a  plane  surface.  If  the  calculation  is  carried  to  10°  each 
way,  as  in  Fig.  72,  equal  to  a  space  of  about  five  inches  on  the  page 
of  the  book,  the  result  is  nearly  the  same,  but  the  curve  is  somewhat 
greater  as  we  approach  the  periphery  of  the  field  of  vision. 

This  gives  us  the  position  of  the  page  in  relation  to  the  plane 


188 


PHYSIOLOGY. 


of  regard  in  which  the  horopter  is  most  completely  formed  and  we 
find  that  the  page  is  tilted  about  15°  beyond  the  right  angle  with  the 
plane  of  regard,  or  at  about  105°.  We  have  found  only  the  direction 
of  the  horizontal  and  vertical  meridians  of  the  horopter,  but  any 
other  meridian  may  be  found  in  a  similar  manner. 

An  interesting  and  very  simple  experiment  for  those  who  are 
able  to  unite  stereoscopic  figures  by  convergence  without  the  aid  of 
a  stereoscope  beautifully  confirms  the  above  calculation. 


Fig.  72. 


Draw  two  vertical  lines  parallel  and  at  a  distance  of  two  and 
one-half  inches  from  each  other  on  a  card  board.  (Fig.  73.) 

Hold  the  card  board  so  that  in  fixing  the  center  of  the  lines 
the  gaze  is  directed  downward  35°.  Hold  the  card  board  twenty-eight 
inches  from  the  eyes. 

One  who  is  expert  with  such  exercises  will  be  able  to  unite  the 
two  lines  at  the  distance  of  fourteen  inches  from  the  eyes. 

If,  instead  of  permitting  a  perfect  union  of  the  lines  in  the 
stereoscopic  image  they  are  held  at  about  one-eighth  of  an  inch 


THE  HOROPTER. 


189 


asunder  it  will  be  easy  to  find  at  what  angle  the  board  must  be  held 
to  render  the  two  stereoscopic  images  exactly  parallel. 

In  my  own  case  I  find  by  numerous  experiments  and  careful 
measurements  that  the  board  must  be  tilted  forward  as  nearly  as 
can  be  ascertained  exactly  15°. 

I  have  1°  of  declination  of  the  right  eye,  which  would  have  little 
influence  on  the  experiment. 

Thus  mathematical  and  experimental  research  lead  to  practically 
the  same  result  in  locating  this  horopter.  By  the  formula  given  we 
may  locate  any  horopter  in  the  median  plane.  In  other  planes  the 
formula  will  be  modified. 

Without  discussing  the  application  of  these  principles  to  space 


Fig.  73. 

perception,  a  field  of  much  interest  and  in  which  many  empirically 
known  facts  in  art  and  in  architecture  may  be  analytically  tested, 
only  brief  space  remains  to  allude  to  the  more  practical  application 
of  the  horopter. 

All  the  discussion  which  has  preceded  has  been  based  upon  the 
assumption  that  the  adjustments  of  the  eyes  are  typical  in  the  sense 
of  being  the  most  favorable  to  the  function  of  combining  the  images 
of  the  two  eyes  in  a  horopter. 

In  real  life  anomalous  conditions  of  adjustments,  conditions 
which  interpose  difficulties  in  forming  perfect  horopters,  are  of  ex- 
treme frequency. 

These  anomalous  conditions  may  act  as  slight  hindrances  or  they 
may  prevent  any  but  an  imperfect  horopter  from  being  formed. 

Let  us  consider  some  of  these. 

It  has  been  seen  that  with  a  given  depression  of  the  plane  of 
regard  and  a  given  convergence  a  horopter  is  formed  in  a  position 


190  PHYSIOLOGY. 

which  can  be  predicated  when  these  two  elements  and  the  length  of 
the  base  line  between  the  nodal  points  are  known.  The  depression  of 
the  plane  of  regard  is  controlled  by  an  impulse  which  is  not  acci- 
dental or  ephemeral,  but  which  is  automatic  and  uniform  for  dif- 
ferent persons  for  the  same  depression  under  like  circumstances. 

Suppose  a  person  whose  eyes  are  so  adjusted  that  with  the  mini- 
mum of  impulse  to  the  governing  muscles  they  are  directed  8°  or  10° 
of  arc  above  the  plane  of  best  adjustment.  Among  people  of  ISTew 
England  ancestry  this  is  almost  a  characteristic,  as  it  is  with  some 
other  groups  of  people.  It  is  not  a  disease,  it  is  the  normal  devel- 
opment from  a  certain  form  of  cranium. 

Suppose  again  that  this  person  takes  a  book  in  hand  to  read. 
He  holds  it  in  the  position  and  at  the  distance  which  we  have 
assumed  for  our  third  horopter.  Is  it  not  plain  that  this  person 
must  not  only  depress  the  plane  of  regard  the  35°  assumed,  but  that 
he  must  also  induce  an  additional  depression  of  8°  or  10°  as  the  case 
may  be? 

This  extra  depression  at  once  automatically  induces  a  greater 
tilting  of  the  meridians.  No  horopter  can  then  be  formed.  To 
remedy  the  difficulty  in  a  measure  the  person  may  throw  the  head 
forward  10°,  but  in  so  doing  there  is  some  disturbance  of  the  equilib- 
rium of  the  muscles,  hence  even  with  this  concession  the  horopter, 
which  will  be  better  than  before,  may  still  be  somewhat  imperfect. 

In  several  papers  I  have  shown  that  as  a  matter  of  fact  people 
with  this  adjustment  of  the  eyes  do  throw  the  head  forward  and  the 
bending  of  the  neck  is,  other  things  being  equal,  in  proportion  to  the 
excess  of  the  normal  upward  direction  of  the  eyes.  We  will  return 
to  this  presently. 

A  second  condition  which  may  interfere  with  the  formation  of 
a  horopter  in  the  appropriate  position  is  in  direct  contrast  to  this. 
The  eyes  may  be  adjusted  so  that  the  plane  of  vision  is  normally 
directed  low. 

Suppose  one  whose  eyes  are'  10°  too  low.  By  the  same  reasoning 
as  before  we  see  that  because  the  dynamic  depression  of  the  gaze 
would  be  less  than  in  the  typical  adjustment,  the  tilting  of  the 
retinal  meridians  would  be  insufficient  for  the  horopter,  and  such 
a  person  must  force  the  chin  high  in  the  air  in  order  to  be  obliged 
to  depress  the  gaze  sufficiently  to  induce  the  necessary  torsion. 

I  have  written  of  these  conditions  and  writers  have  interpreted 
ihe  difficulty  as  a  strain  on  the  muscles  of  depression  or  elevation. 


THE  HOROPTER.  191 

This  is  an  entire  misapprehension.  It  does  not  follow  that  there 
is  any  considerable  strain  on  the  muscles  of  adjustment,  but  the  head 
must  be  placed  in  position  in  which  the  automatic  torsions  shall  in 
some  measure  correspond  to  the  direction  of  the  gaze. 

A  third  form  of  hindrance  to  the  constitution  of  the  horopter 
is  found  in  the  condition  which  I  have  called  declination. 

This  consists  of  an  anomalous  leaning  of  the  meridians  of  one 
or  both  eyes.  It  is  a  very  common  defect  and  results  in  great  per- 
plexity to  the  adjusting  muscles.  Its  practical  importance  is  greater 
than  those  conditions  already  mentioned.  It  may  induce,  like  the 
two  conditions  named,  a  throwing  forward  or  a  tipping  backward  of 
the  head,  or  of  the  head  to  one  side,  depending  on  the  direction, 
symmetry,  or  degree  of  the  declination  defects  in  the  two  eyes.  All 
that  has  been  said  about  the  forward  and  backward  holding  of  the 
head  in  the  other  conditions  may  apply  to  these  cases,  and  in  some 
instances  the  unnatural  pose  of  the  head  and  body  from  this  cause 
are  extreme.  Since  1887  I  have  in  various  articles  called  attention 
to  these  unfavorable  positions  of  the  head  and  body,  and  as  the  knowl- 
edge of  the  nature  of  the  anomalous  adjustments  has  gradually  devel- 
oped, the  relations  between  them  and  these  abnormal  positions  of  the 
body  have  been  more  clearly  understood. 

Eecall  the  case  of  the  person  whose  eyes  are  adjusted  for  too 
high  a  plane.  The  head  is  thrown  forward  as  part  of  the  automatic 
process  of  adjustment.  The  larynx  is  partly  closed,  the  chest  is 
sunken.  Air  passes  less  freely  to  the  lungs  than  it  would  were  the 
head  held  erect.  It  is  among  this  class  of  people  that  consumption 
commits  its  ravages.  There  are  few,  if  any,  consumptives  who  do 
not  have  a  high  adjustment  of  the  eyes  or  a  form  of  declination  which 
induces  a  corresponding  head  position. 

Then  there  is  the  person  whose  eyes  are  adjusted  for  too  low  a 
plane  and  whose  head  is  thrown  back. 

It  is  with  this  class  of  persons  and  with  those  whose  declina- 
tions induce  a  similar  pose  that  the  occipital  neuralgias,  pains  in 
back  of  the  head  and  neck  and  in  the  lumbar  region  are  principally 
found.  The  number  of  such  persons  is  enormous  and  the  suffering 
from  this  cause  infinite. 

From  this  cause  also,  the  head  being  thrown  back,  the  vertebral 
column  often  bends  in  toward  the  front,  inducing  not  only  the  mus- 
cular pains  just  mentioned,  but  even  a  change  in  the  cartilages  be- 


192  PHYSIOLOGY. 

tween  the  vertebrae,  thus  inducing  a  chronic  convexity  of  the  spinal 
column. 

Thus,  also,  when,  to  form  a  complete  horopter,  the  head  is 
thrown  to  one  side,  as  it  often  is  with  hyperphoria,  or  with  certain 
combinations  of  declination,  there  occur  compensating  directions  of 
the  body  which  induce  lateral  curvatures  which,  by  long  custom, 
reduce  the  energy  of  some  muscles,  while  in  others  a  state  of  un- 
natural tension  becomes  habitual,  with  the  result  of  chronic  lateral 
curvatures. 

To  such  contingencies  I  long  ago  called  attention,  and  it  need 
only  be  said  that  the  conditions  above  mentioned  are  only  examples 
of  the  distinct  effects  which  may  and  often  do  extend  to  the  pelvis  and 
to  the  extremities. 

From  declinations  which  do  not  induce  false  carriage  of  the 
head  arise  perplexities  in  adjusting  for  the  horopter  which  result  in 
headaches,  dyspepsias,  and  a  long  array  of  nervous  ills. 

A  subject  whose  importance  cannot  well  be  overestimated  has 
been  presented  in  this  brief  outline.  It  is  worthy  of  the  most  careful 
research  and  minute  attention. 

Many  of  the  nervous  symptoms,  pain,  spasm,  etc.,  which  I  at  the  time 
of  the  publishing  of  my  work  on  "Functional  Nervous  Diseases"  (1883)  re- 
garded as  reflex  are,  in  fact,  direct  results  of  muscular  tension  or  of  injury 
to  or  impairment  of  the  functions  of  certain  nerves  as  the  result  of  the  pose  of 
the  head  or  body,  which  is  the  result  of  unfavorable  adjustments  of  the  eyes, 
and  sometimes  from  pressure  upon  or  extension  of  nerves  as  a  result  of  mus- 
cular tensions  in  the  more  immediate  vicinity  of  the  eyes. 

Among  nervous  phenomena  of  the  first  class  may  be  mentioned  the 
habitual  pains  in  the  back  of  the  head,  that  in  the  region  of  the  spine  of  the 
seventh  cervical  vertebra,  that  under  the  angle  of  the  shoulder  blades,  and 
also  that  in  the  lumbar  region,  which,  for  almost  time  out  of  mind,  has  in  the 
case  of  women  been  attributed  to  organic  displacements. 

To  these  may  be  added  the  chronic  pain  often  experienced  in  the  shoulder, 
generally  the  left,  running  down  the  arm.  So  also  we  might  add  a  number 
of  forms  of  pain,  spasm  or  impaired  functional  activity.  Some  of  these  symp- 
toms, such  as  the  pains  in  the  muscles  at  the  side  of  the  neck,  were  correctly 
attributed  to  the  tension  on  those  muscles  due  to  the  carriage  of  the  head  to 
one  side  in  hyperphoria. 

Among  the  nervous  manifestations  of  the  second  class  may  be  mentioned 
a  symptom  which  has  interested  me  for  a  long  time,  and  which  I  was  confident 
must  be  a  result  of  ocular  maladjustments,  since  it  regiilarly  disappeared  with 
appropriate  treatment  to  these  faults.  I  refer  to  the  chronic  and  often 
severe  pain  experienced  by  many  persons  at  the  vertex  of  the  head.  This  is  a 
distressing  symptom  to  a  large  number  of  persons. 


THE  HOROPTER.  193 

I  am  now  convinced  that  this  pain  is  a  manifestation  of  the  pressure  of 
the  brows  against  the  supra-orbital  nerve  as  it  turns  over  the  border  of  the 
orbit  and  that  the  painful  sensation  is  experienced,  not  at  the  point  of  pres- 
sure, but  in  the  region  of  the  distribution  of  the  nerve. 

It  is  easy  to  account  for  pains  in  the  muscles  more  immediately  surround- 
ing the  eye  and  the  orbit,  but  the  facial  neuralgias  which  are  not  unfrequently 
the  results  of  faulty  eye  adjustments  are  not  so  readily  accounted  for  on  this 
mechanical  principal.  A  careful  consideration  will,  however,  enable  one  to 
locate  the  source  of  irritation  in  nearly  all  these  cases,  and  I  have  no  doubt 
that  most  of  these  facial  neuralgias  have  for  their  original  cause  some  pres- 
sure of  or  extension  of  nerves  directly  or  indirectly  from  the  efforts  to  adjust 
the  eyes. 

There  are  also  much  more  distant  and  at  first  thought  much  less  proba- 
ble nervous  reactions  from  these  ocular  causes  which,  while  it  is  certain  that 
they  are  in  some  -way  distinctly  related  to  these  ocular  efforts,  it  is  not  so 
easy  to  trace  the  line  of  association.  Many  years  ago,  in  my  essay  presented 
to  the  Royal  Academy  of  Medicine  of  Belgium  (1883),  I  mentioned  dyspepsia, 
constipation,  and  irregularities  in  the  action  of  the  heart  as  among  the  distant 
manifestations  of  ocular  conditions.  That  dyspepsia  in  various  forms  is,  not 
occasionally,  but  generally,  a  manifestation  of  results  of  anomalous  ocular 
adjustments,  has  for  many  years  been,  in  my  mind,  an  established  fact.  No 
less  may  be  said  of  habitual  constipation.  These  manifestations  then  must  be 
either  of  reflex  nature  or  a  result  of  mechanical  influence  upon  certain  nerves. 

Since  my  early  observations  of  the  pose  of  the  head  in  relation  to  the 
adjustments  of  the  eyes  I  have  been  struck  by  the  very  frequent  association 
of  dyspeptic  symptoms  with  the  condition  of  a  depression  of  the  planes  of  vision 
or  with  the  corresponding  pose  of  the  head  from  declination.  The  cases  are 
not  by  any  means  confined  to  persons  with  this  pose  of  the  head,  but  the 
large  proportion  of  cases  in  which  there  is  this  association  is  most  noticeable. 

To  account  for  this,  from  the  mechanical  point  of  view  it  is  quite  sup- 
posable  that  by  reason  of  the  relation  of  the  pneumogastric  nerve  to  the  com- 
mon carotid  artery  and  the  jugular  vein  as  the  nerve  descends  through  the 
neck,  lying  between  these  two,  one  being  in  front,  the  other  behind,  a  habitual 
position  of  the  head  in  which  it  is  thrown  somewhat  backward  might  induce  a 
pressure  by  these  two  great  vessels  which  might  interfere  with  the  conductiv- 
ity of  the  great  nerve,  important  branches  of  which  are  distributed  to  the  heart 
and  stomach. 

This  view  is  advanced  as  a  possible  hypothesis  and  not  as  an  established 
proposition. 

It  would  be  less  easy  to  trace  the  direct  cause  of  the  nervous  disturb- 
ance in  chronic  constipation,  but  it  seems,  when  these  other  facts  are  con- 
sidered, quite  reasonable  to  suppose  that  some  similar  mechanical  cause  may 
be  suspected.  The  relation  between  the  nervous  condition  and  the  adjust- 
ments of  the  eyes  is  in  no  doubt.  It  is  not  so  evident  through  what  channel 
the  nervous  relation  is  established. 

It  is  not  the  purpose  of  this  work  to  enter  upon  theories  of  disease,  but 
this  view  of  a  mechanical  origin  of  many  of  the  symptoms  which  I  previously 


194  PHYSIOLOGY. 

regarded  as  reflex  appears  to  me  to  deserve  a  place  in  a  work  devoted  to  the 
motor  apparatus  of  the  eyes. 

These  views  respecting  the  more  purely  mechanical  effects  arising  from 
anomalous  adjustments  of  the  eyes  do  not  disavow  but  are  quite  consistent 
with  a  belief  in  the  reflex  influence  from  the  eyes.  They  indicate  that  some 
of  the  phenomena  which  were  included  in  that  belief  are  removed  to  another 
field,  and  it  is  not  impossible  that  many  other  phenomena  may  at  length  be 
explained  as  the  more  direct  and  immediate  influences  of  the  motile  apparatus 
of  the  eyes  in  adjusting  for  the  horopter. 


SECTION  XXII. 

THE  DIRECTIONS  OF  THE  APPARENT  VERTICAL  AND  HORIZONTAL 

MERIDIANS.1 

COMPARISONS  OF  DATA  EEGARDING  THE  EETINAL  MERIDIANS. 

If  the  point  of  regard  of  the  two  eyes  is  fixed  in  the  median  and 
in  the  horizontal  plane  and  at  infinite  distance  while  the  head  of  the 
observer  is  in  the  primary  position,  it  might  be  assumed  that  the  ver- 
tical meridians  of  each  retina  would  coincide  with  a  plane  perpendic- 
ular to  the  plane  of  regard,  and  that  the  horizontal  meridian  would 
coincide  with  the  plane  of  regard. 

In  respect  to  a  proposition  so  apparently  simple  and  involving 
important  questions,  practical  as  well  as  theoretical,  the  views  of  the 
ablest  investigators  have  been  at  variance.  While  Helmholtz  concedes 
that  the  horizontal  retinal  meridians  so  nearly  coincide  with  the  plane 
of  regard  that  they  may  be  considered  as  practically  identical  with  it, 
he  characterizes  the  vertical  meridians  as  "apparent"  vertical  meri- 
dians, and  he  reasons,  from  his  own  experiments  and  those  of  Volk- 
mann,  that  these  apparently  vertical  meridians,  as  a  matter  of  fact, 
in  normal  eyes,  converge  downwards  to  the  extent  of  l1/^0  each,  making 
thus  an  angle  between  the  vertical  meridians  of  the  two  eyes  of  21/2°> 
with  the  lower  extremities  of  the  meridians  approaching  each  other.2 

Basing  his  calculations  on  this  proposition  and  on  the  law  of 
Listing,  Helmholtz3  deduced  his  remarkable  demonstration  of  the 
horopter. 


1  My  first  exposition  of  this  subject  was  published  in  Archives  of  Oph- 
thalmology, No.  2,  1897,  more  at  length  than  in  this  section. 

2  Nevertheless,   Helmholtz   concedes,   incidentally,   that   others   may   not 
have  the   same  inclination   of  the  vertical  meridians   as   his   own.     "Optique 
Physiol.,"  p.  732. 

3  Loc.  cit.,  p.  900. 


DIRECTIONS  OF  RETINAL  MERIDIANS.  195 

Meisner1  also  found,  as  he  believed,  a  tilting  of  the  apparent  ver- 
tical meridians,  but  worked  out  a  different  theory  of  the  horopter. 

Hering2  found  a  rolling  of  all  the  meridians  of  his  own  eyes  and 
arrived  at  a  conclusion  that  this  was  true  of  all  eyes. 

Le  Conte3  thought  that  he  had  found  the  vertical  meridians  in  his 
own  case  vertical,  but  his  experiments  were  not  so  conducted  as  to  be 
at  all  conclusive  of  his  own  position. 

A  subject  of  much  physiological  interest  has  been  thus  thrown  into 
confusion  by  the  variation  of  data  from  which  learned  investigators 
have  drawn  their  conclusions. 

All  these  divergencies  of  results  and  of  opinions  have  arisen  from 
imperfect  methods  of  investigation,  and  generalizations  have  been 
based  on  the  unwarranted  assumption  that  each  observer,  without  an 
examination  of  the  adjustments  of  his  own  eyes,  was  able  to  say  that 
what  appeared  to  be  a  rule  for  him  must  also  be  a  rule  for  all  others 
with  normal  eyes,  and  by  "normal  eyes"  was  meant  eyes  which  could 
see  fairly  well  with  proper  glasses.  It  has  been  as  though  a  surveyor 
had  made  careful  triangulations  of  all  the  hilltops  in  view,  but  had 
neglected  to  locate  the  eminences  from  which  the  base  line  for  his 
triangulations  was  made. 

After  the  determination  of  an  exact  method  for  examining,  the 
first  necessity  in  an  inquiry  respecting  the  vertical  meridians  is  an 
absolute  understanding  of  the  adjustments  of  the  eyes  of  the  observer. 
The  fact  that  one  sees  well  is  only  a  single  element  in  the  problem.  Is 
there  a  condition  of  declination,  of  heterophoria,  of  anophoria,  or  of 
katophoria?  These  and  other  questions  in  the  same  line  are  essential 
elements  of  the  inquiry,  and  unless  a  statement  of  the  conditions  of  the 
eyes  in  respect  to  each  of  these  elements  is  included  in  the  report  of 
examinations  in  this  field,  observations  have  much  the  same  value  as 
the  triangulations  of  the  surveyor  above  supposed. 

The  question  of  the  normal  adjustments  of  the  plane  of  regard  of 
the  individual  with  respect  to  the  primary  position  of  his  own  head 
when  the  minimum  of  nervous  energy  is  directed  to  the  muscles  of  the 
eyes,  was  not,  previous  to  my  own  investigations,  taken  into  account 
in  the  experiments  of  those  who  have  interested  themselves  in  the 
problems  of  corresponding  points  of  the  retinas  and  of  the  horopter, 
nor  were  questions  of  declination  or  of  heterophoria. 


1  "Physiologic  des  Seeorgans." 

2  "Beitrage  Zur  Physiologic,"  p.  175 ;    Archiv  f iir  Ophthal.,  Bd.  xv,  Abth., 
1,  S.  1. 

3  "Sight,"  p.  223. 


196  PHYSIOLOGY. 

In  the  section  on  the  normal  directions  of  the  planes  of  vision  in 
relation  to  cranial  characteristics  it  will  be  shown  that  the  eyes  of  many 
persons  are  normally  adjusted  much  above  the  horizontal  plane,  that 
a  deviation  of  8°  or  10°  of  arc  above  the  horizontal  plane  is  not 
very  unusual,  anoTthat  there  is  another  large  class  of  persons  in  whom 
the  deviation  of  the  plane  of  normal  direction  of  the  eyes  is  materially 
below  the  horizontal  plane. 

It  need  hardly  be  said  that,  in  an  investigation  in  which  the  law 
of  Listing  plays  the  principal  role,  such  peculiarities  must  be  taken 
into  consideration,  and  that,  in  the  absence  of  a  due  regard  to  the 
normal  plane  of  direction  as  shown  by  the  tropometer,  there  can  be, 
as  there  have  been,  only  confusion  and  results  of  uncertain  value  from 
the  researches  of  investigators. 

The  requisites,  then,  for  determining  the  actual  position  of  the 
meridians,  a  suitable  method  having  been  chosen,  are: — 

1.  A  knowledge  on  the  part  of  the  observer  of  the  adjustments 
of  his  own  eyes  in  respect  to  heterophoria,  anophoria,  or  katophoria,. 
and  especially  in   respect  to   the  conditions  known   as   declinations. 
Since  the  introduction  of  the  clinoscope  it  is  a  matter  of  daily  experi- 
ence that  anomalies  in  the  directions  of  the  meridians  in  individual 
cases  are  even  more  frequent  than  those  anomalies  which  take  the  forms 
of  heterophoria.    It  no  more  follows  that  because  of  such  anomalies  of 
declination  it  is  impossible  to  arrive  at  a  correct  idea  of  the  ideal 
position  of  the  meridians  than  that,  because  of  the  anomalies  of  hetero- 
phoria, it  is  impossible  to  arrive  at  a  just  idea  of  orthophoria. 

2.  A  means  by  which  the  exact  position  of  the  head  may  be  main- 
tained.   The  position  described  by  Volkmann,  Helmholtz,  and  others 
is  inexact,  uncertain,  and  irregular.    Accurate  data  can  hardly  be  ex- 
pected in  this  field  of  inquiry  when  the  position  of  the  head  of  the 
observer  is  that  which  he  happens  to  think  at  the  moment  is  his  pri- 
mary position. 

3.  Examinations  in  this  field  of  inquiry  when  the  observer  can 
see  surrounding  objects  are  of  little  if  of  any  value.     The  instinct  to- 
correct  a  leaning  of  the  meridians  when  surrounding  objects  would 
otherwise  appear  to  lean  is  as  great  as  the  instinct  to  converge  when 
the  eyes  are  directed  at  a  near  point.     Hence  all  objects  but  the  test 
object  must  be  eliminated  from  the  field  of  regard. 

4.  "When  it  is  desirable  to  blend  or  compare  test  objects  in  the 


DIRECTIONS  OF  RETINAL  MERIDIANS.  197 

field  of  regard  of  the  two  eyes  as  for  the  distant  point,  the  blending  or 
comparison  should  be  made  with  the  lines  of  regard  of  the  two  eyes 
parallel.  This,  of  course,  cannot  be  accomplished  by  the  ordinary  form 
of  stereoscope,  and  it  cannot  be  done  when  stereoscopic  images  are 
blended  by  converging  the  eyes  without  -the  intervention  of  the  stereo- 
scope. 

All  the  conditions  for  physiological  research  in  respect  to  the 
meridians  when  the  lines  of  regard  are  parallel,  are  met  by  the  clino- 
scope,  which  is  described  in  the  section  on  "Declinations." 

In  the  practical  work  of  the  consulting-room,  for  examinations 
of  anomalies  of  declination,  the  instrument  is  furnished  with  a  single 
set  of  test  objects  which,  in  order  that  they  may  be  always  accurately 
adjusted,  are  not  easily  interchangeable  with  others.  For  the  pur- 


EB.MEYROWirZ.NX 

Fig.  74. — Clinoscope  Objectives. 

poses  of  physiological  investigations  the  instrument  is  supplied  with 
a  number  of  these  haploscopic  diagrams  and  these  can  be  multiplied 
at  the  desire  of  the  investigator. 

A  modified  instrument  with  short  tubes,  permitting  convergence 
within  a  few  inches  of  the  eyes,  has  now  replaced  the  older  form,  per- 
mitting examinations  of  a  more  precise  character. 

The  pair  of  diagrams  first  represented  (Fig.  74)  is  the  pair  in 
use  for  clinical  purposes.  It  is  also  important  in  physiological  re- 
search. 

As  the  trained  observer  looks  into  the  tubes  the  two  discs  blend 
and  the  two  pins  become  one  long  pin  with  the  head  in  the  middle. 
When  each  pin  is  brought  to  the  position  that  it  appears  to  the  observer 
to  be  exactly  vertical  and  remains  so,  it  marks  the  position  of  the 
vertical  meridian  of  the  observer's  eye  (except  as  it  is  controlled  by 
automatic  tension)  as  indicated  by  the  pointer  and  scale  above  the  tube 
for  that  eye. 


198 


PHYSIOLOGY. 


Another  pair  of  diagrams  which  is  useful  in  testing  the  doctrine 
of  Helmholtz,  that  the  vertical  meridians  lean  while  the  horizontal 
meridians  are  strictly  horizontal,  is  shown  at  Fig.  75.  Here  both 
vertical  and  horizontal  lines  are  included  in  the  combined  figure.  In 
the  discs  themselves  the  lines  represented  here  by  black  dots  consist 
of  series  of  faint  red  dots.  The  perfect  union  of  both  the  vertical  and 
horizontal  lines,  which  can  be  effected  by  persons  with  good  adjust- 
ments, would  not  confirm  the  view  of  Helmholtz. 

As,  by  the  aid  of  such  diagrams  the  observer  is  enabled  to  unite 
the  figures  without  the  aid  of  convergence  or  divergence  and  without 
the  aid  of  prisms  or  mirrors,  and  as  the  environments  are  so  far  shut 
out  as  to  remove  the  suggestion  of  verticality  and  horizontality  except 
as  they  are  associated  with  the  general  muscular  adjustments  of  the 


E.B.MEYROWITZ.N.Y. 


Fig.  75. 


body,  the  experiments  of  Hering,  Volkmann  and  Helmholtz  can  be 
made  under  correct  conditions. 

If  the  observer  has  found  that  his  eyes  are  adjusted  for  a  plane 
above  the  horizon,  either  the  tubes  of  the  instrument  should  be  so 
adjusted  as  to  allow  for  this  amount  of  upward  adjustment  of  the  eyes 
or  some  other  suitable  provision,  as,  e.g.,  the  use  of  prisms  or  an  allow- 
ance for  the  defect,  is  to  be  made.  The  rule  holds  when  the  tropo- 
meter  shows  an  adjustment  of  the  eyes  for  a  plane  below  the  horizon. 

In  respect  to  my  own  ocular  adjustments,  after  a  great  number 
of  examinations,  continued  through  many  years,  I  have  failed  to  find 
even  a  slight  degre  of  esophoria,  exophoria,  or  hyperphoria;  and  the 
examinations  made  since  the  introduction  of  the  tropometer  have  not 
shown  that  the  eyes  are  adjusted  for  a  plane  either  above  or  below 
the  horizon.  There  is  declination,  right,  +  1°  >  left,  0°. 

Thus,  experiments  in  my  own  case  in  regard  to  the  direction  of 
the  apparent  vertical  meridians  should  be  conducted  with  the  tubes 
of  the  clinoscope  directed  horizontally. 


DIRECTIONS  OF  RETINAL  MERIDIANS. 


199 


When  the  question  of  a  perfect  union  of  exactly  vertical  and 
exactly  horizontal  lines  simultaneously  in  the  clinoscope  is  investi- 
gated, my  own  observations  do  not  correspond  with  the  results  reported 
by  Helmholtz,  nor  do  I  find  that  others  who  have  no  important  errors 
of  adjustments  have  any  difficulty  in  blending  lines  which  are  exactly 
at  right  angles. 

The  well-known  diagram  of  Helmholtz,  representing  the  direc- 
tions of  vertical  and  horizontal  lines,  which  he  regarded  as  necessary 
for  complete  union  in  his  own  case,  induces  confusion  of  one  or  other 
sets  of  lines  in  my  own  experience  and  in  that  of  all  others  with  fairly 
good  adjustments  who  have  examined  them  in  my  presence,  if  the 
card  is  held  in  the  primary  position.  But  if  the  diagram  is  held  so 
that  the  gaze  is  directed  downward  about  30°  while  I  unite  the  two 


E.BMEYROWITZ.H.Y. 

Fig.  76. — Helmholtz's  Squares. 

halves  of  the  figure  by  convergence,  the  black  and  white  lines  coin- 
cide exactly. 

All  of  my  experiments,  which  have  now  been  continued  during 
several  years,  lead  to  the  conclusion  that  the  typical  normal  position 
for  the  vertical  meridians  is  the  exactly  vertical  position,  and  that  the 
typical  position  of  the  horizontal  meridians  corresponds  with  the 
external  horizon. 

Deviations  from  these  positions  when  the  regard  is  directed  in 
the  primary  position  are  anomalies,  and  are  to  be  studied  as  such. 

The  passing  of  the  meridians  from  the  vertical  and  horizontal 
positions  in  making  various  adjustments  of  the  eyes,  is  also  a  subject 
for  study  by  itself. 

The  subject  of  the  position  of  the  meridians  is  treated  at  more 
length  in  my  article  which  appeared  in  Archives  of  Ophthalmology, 
No.  2,  1897. 


200  PHYSIOLOGY. 

SECTION  XXIII. 

VOLUNTARY  TORSION  AND  ITS  PHYSIOLOGICAL  EFFECTS. 

When  the  eyes  are  turned  to  one  side  and  upward  or  downward, 
there  occurs  also,  as  we  have  seen  in  the  section  on  "Torsions,"  an 
apparent  rotation  on  the  optic  axes.  This  peculiar  apparent  rotation 
of  the  eyes  is  not  necessarily  made  as  an  independent  movement,  for 
it  depends  upon  the  passing  of  the  eyes  from  one  fixed  position  to 
another,  and  the  consequent  change  in  the  relation  of  the  cornea  to 
the  cranium. 

But  there  is  required  in  directions  of  the  line  of  regard  other 
than  these  oblique  directions  just  mentioned,  an  actual  turning  upon 
the  optic  axes. 

It  is  a  fact  long  familiar  to  students  of  physiological  optics  that 
this  power  of  torsion  may  be  demonstrated  in  a  number  of  ways,  con- 
venient among  which  is  that  of  the  uniting  of  linear  figures  with  the 
stereoscope  and  giving  to  one  of  the  figures  a  gradual  turn.1  The 
images  will  for  a  time  continue  united,  but  at  length,  when  the  rotation 
of  the  figure  has  been  carried  as  far  as  the  rotation  of  the  eyes  on  the 
optic  axes  can  follow,  the  images  will  separate.  If,  while  the  images 
of  the  two  sides  of  the  stereoscopic  card  are  held  united,  but  when 
the  parallelism  of  the  vertical  lines  is,  to  a  considerable  extent,  lost, 
the  observer  closes  the  eyes  for  a  moment  and  then  opens  them,  the 
images  will  be  seen  double,  with  the  vertical  lines  diverging  above  or 
below.  After  a  little,  the  images  may  again  adjust  themselves  and 
complete  union  may  be  re-established. 

While  the  rotation  thus  demanded  may  be  isolated  from  the  move- 
ments with  which  it  is  usually  associated,  it  is  not,  under  ordinary 
conditions.,  possible  to  isolate  the  action  of  a  single  pair  of  muscles 
for  its  production. 

As  to  the  extent  to  which  such  voluntary  torsion  can  be  carried 
it  is  greater  in  convergence  than  in  parallelism  of  the  eyes.  Hence, 
it  is  greater  when  the  ordinary  form  of  stereoscope  is  used  for  its 
determination  than  when  the  images  of  the  two  eyes  are  caused  to 
blend  without  an  instrument,  or  when  some  instrument  is  employed 
which  does  not,  like  the  Brewster  stereoscope,  induce  convergence. 

For  examination  of  the  power  of  voluntary  torsion  the  clinoscope 


See  foot  note,  page  201. 


VOLUNTARY  TORSION. 


201 


affords  a  means  attended  by  a  much  greater  degree  of  facility  and  of 
accuracy  than  any  which  has  been  suggested.1  In  using  the  instru- 
ment for  this  purpose  the  lines  which  cross  but  half  the  field  are  no 
longer  useful.,  but  straight  lines,  crossing  the  middle  of  the  field  and 
extending  to  its  extremities  (Fig.  77),  are  required. 

If  such  lines  are  adjusted  vertically  and  the  two  discs  caused  to 
blend  and  the  tubes  are  then  rotated,  each  in  the  positive  direction 
(upper  extremities  of  the  lines  outward),  the  mental  conception  of 
the  position  of  the  line  formed  by  the  union  of  the  two  is  modified 
in  an  interesting  manner.  As  soon  as  the  tubes  are  thus  rotated  out- 
ward, the  line,  so  long  as  it  is  held  as  a  single  line,  begins  to  assume 
a  direction  approaching  the  horizontal.  The  lower  extremity  points 
in  toward  the  observer  and  the  upper  extremity  outward  from  the 
tube.  If  the  observer  has  good  powers  of  voluntary  torsion,  the  line 


Fig.  77. — Torsion  Objectives. 

will  at  length  appear  to  point  almost  horizontally  and  directly  in  and 
out,  and  to  be  materially  elongated,  as  though  an  arrow  were  to  be 
shot  outward  and  slightly  upward. 

With  a  good  power  of  such  torsion,  the  lines  may  be  held  in 
union  in  the  positive  direction  until  each  of  the  pointers  marks  11°. 
Thus,  between  the  vertical  retinal  meridians  of  the  two  eyes  an  angle 
of  22°,  with  its  apex  down,  may  be  formed. 

If  the  rotation  is  carried  in  the  negative  direction,  a  torsion  of 
about  an  equal  extent,  or  possibly  2°  or  3°  less,  is  induced,  and,  in 
this  case,  the  line  assumes  again  an  approximation  to  the  horizontal 
position,  not  pointing  from  within  outward  and  upward,  but  outward 
and  downward. 


1  In  1861,  Professor  A.  Nagel  investigated  the  voluntary  rotations  about 
the  optic  axis  by  experiments  with  the  stereoscope  ("Das  Sehen  mit  zwei 
Augen,"  Leipzig).  Later,  by  other  methods,  Helmholtz  investigated  the  same 
phenomena.  Neither  of  the  methods  was,  for  various  reasons,  exact,  or  could 
attain  to  any  more  than  approximate  results. 


202  PHYSIOLOGY. 

If  one  is  able  to  induce  with  the  clinoscope  a  torsion  of  20°  with 
the  two  eyes,  he  cannot  (at  least,  this  is  true  for  the  cases  which  I 
have  examined),  while  maintaining  the  vertical  position  of  one  of  the 
lines  of  the  clinoscope,  rotate  the  other  to  an  extent  equal  to  that 
to  which  the  two  were  rotated.  I  find  that  with  one  line  remaining 
vertical,  I  can  rotate  the  other,  either  in  the  positive  or  negative 
direction,  about  14°,  which  is,  however,  more  than  half  of  what  I  can 
accomplish  with  equal  rotations  of  both  tubes. 

If  the  right  tube  remains  with  the  vertical  line  at  0°  and  the  left 
tube  is  caused  to  rotate  outward,  the  combined  image  points  outward, 
upward,  and  to  the  left.  If  the  left  tube  is  stationary  at  0°  and  the 
right  tube  rolls  out,  the  line  points  outward,  upward,  and  to  the  right. 

It  is  an  interesting  as  well  as  an  important  practical  fact,  and 
one  to  which  little  if  any  attention  has  been  given  until  my  own  in- 
vestigations,1 that  horizontal  lines  cannot  be  held  in  union  while 
being  rotated  from  the  horizontal  direction  to  an  extent  nearly  equal 
to  that  in  which  vertical  lines  can  be  held  in  union.  If  vertical  lines 
can  be  held  in  union  with  a  rotation  of  20°  or  more,  the  horizontal 
lines  usually  become  double,  with  a  total  rotation  for  both  tubes  from 
6°  to  8°.  Indeed,  it  requires  some  practice  to  hold  the  lines  in  union 
with  a  rotation  of  each  tube  either  out  or  in  to  the  extent  of  3°, 
inducing  a  torsion  of  6°. 

If  the  tubes  rotate  out,  the  line  appears  concave,  bending  outward 
at  the  center,  or  convex,  according  to  the  will  of  the  observer.  If  the 
rotations  are  negative  the  line  is  convex  or  concave  as  before. 

The  fact  of  the  difference  in  the  ability  to  hold  vertical  and  hori- 
zontal lines  in  union  can  be  seen  to  constitute  an  important  element 
in  and  to  have  a  bearing  upon  experiments  such  as  those  by  which 
Volkmann  and  Helmholtz  investigated  the  directions  of  the  different 
retinal  meridians.  For  while  there  is  an  imperious  mental  necessity 
for  holding  the  horizontal  lines  approximately  so  in  order  to  unite 
the  two  images,  a  very  considerable  latitude  is  permitted  in  respect 
to  the  position  of  the  vertical  lines,  and  the  torsional  act  may  over- 
come an  important  deviation. 

The  principle  holds  in  binocular  vision  in  the  ordinary  uses  of 
the  eyes.  The  fact  of  difference  in  the  ease  of  torsion  for  horizontal 
and  vertical  lines  has  its  practical  application  in  many  directions.  A 


1  "Directions  of  the  Apparent  Vertical  and  Horizontal  Meridians  of  the 
Retina,  etc."      Stevens,  Archives  of  Ophthalmology,  No.  2,  1897. 


NORMAL  DIRECTIONS  OF  PLANES  OF  VISION.  203 

single  example  may  be  introduced  to  serve  as  an  illustration  of  this 
important  principle.  The  question  of  the  form  and  proportions  of 
printed  type,  in  order  to  produce  the  most  easily  legible  characters, 
has  long  engaged  those  who  are  interested  in  the  progress  of  the  art 
of  printing  in  its  relation  to  the  preservation  of  the  functions  of  the 
eyes.  Experience  has,  independent  of  any  theory,  taught  practical 
men  engaged  in  the  art  of  typography,  that  the  height  of  letters  must 
be  considerably  greater  than  their  breadth.  In  the  ordinary  type 
used  in  America  and  England  the  vertical  length  of  all  the  letters  of 
a  line  aggregates  rather  more  than  thirty  millimeters  to  every  twenty 
millimeters  of  the  breadth  of  letters.  In  the  French  typography  the 
height  of  letters  is  still  greater.  Examinations  of  different  styles  of 
typography  will  convince  a  careful  investigator  that  broad,  low  letters 
are  less  easily  held  in  perfect  binocular  union  than  the  form  more 
nearly  approaching  the  Gothic  style,  and  letters  with  a  large  pro- 
portion of  horizontal  lines  are  less  easily  recognized  than  those  in 
which  the  vertical  lines  predominate.  Thus,  the  letters  /,  p,  d,  and 
w  are  recognized  more  quickly  than  e,  a,  s,  and  c. 


SECTION  XXIV. 

THE  NORMAL  DIRECTION  OF  THE  PLANES  OF  VISION  IN  RELATION 
TO  CERTAIN  CRANIAL  CHARACTERISTICS.1 

In  regard  to  the  ability  of  the  eyes  to  rotate  in  the  vertical  direc- 
tion, I  have  found  that,  under  the  best  conditions,  the  full  extent  of 
the  excursion  amounts  to  about  83°  of  arc,  and  of  this  excursion  about 
50°  is  below  the  horizontal  plane  and  about  33°  above  it.  Of  this 
adjustment,  since  it  induces  no  torsional  effect  when  the  lines  of 
regard  are  in  the  plane  of  the  horizon,  and  does  not  unduly  increase  the 
torsion  in  convergence  with  depression  of  the  plane  of  regard,  since 
it  exercises  no  unfavorable  influence  in  inducing  either  lateral  devia- 
tions or  tendencies  toward  deviations,  and  since  also  practical  experi- 
ence has  shown  it  to  be  the  most  favorable  to  the  continued  use  of  the 
eyes,  it  may  be  said  that  these  rotations  are  associated  with  the  typical 
position  of  the  normal  plane  of  vision. 

If  the  total  excursion  of  the  eyes  remains  of  about  the  same  extent 


1  The   principles   discussed   in   this   section   were  first   announced   in   my 
paper  in  the  Archives  of  Ophthalmology,  No.  3,  1897. 


204  PHYSIOLOGY. 

(83°),  but  if  the  ability  to  rotate  them  upward  is  materially  greater 
than  33°,  that  is,  if  it  equals  or  exceeds  about  37°,  while  the  down- 
ward rotation  is  restricted  to  a  corresponding  extent,  the  normal  visual 
plane  is  directed  so  high  that  at  the  horizon  a  slight  outward  torsion 
is  induced.  A  failure  to  rotate  the  eyes  up  to  the  extent  of,  say,  30°, 
while  the  downward  excursion  is  increased,  indicates  a  depression  of 
the  normal  plane  of  vision.  It  will  be  observed  that  a  margin  of  about 
3°  on  the  side  of  a  restriction  of  upward  rotations  is  regarded  as 
within  the  possible  limits  of  the  most  favorable  condition.  In  many 
cases  this  allowance  appears  to  be  too  great  and  a  failure  of  rotation 
up  to  at  least  32°  appears  to  induce  mechanical  effects  which  in  prac- 
tice are  manifested  in  asthenopic  or  other  nervous  disturbances. 

A  somewhat  greater  limit  in  respect  to  an  excess  of  upward  rota- 
tion appears  to  be  within  the  extent  of  typical  rotations.  Practical 
experience,  however,  proves  that  beyond  a  rotation  of  37°  in  the  up- 
ward direction  a  distinct  torsion  is  induced  in  directing  the  gaze  in 
the  primary  position. 

In  order  to  obtain  exact  and  uniform  measurements  of  the  excur- 
sions of  the  eyes,  the  head  of  the  person  observed  is  to  be  placed  and 
maintained  during  the  examination  in  a  position  such  as  is  indicated 
on  page  226,  where  the  conditions  for  examining  by  the  tropometer  are 
described. 

Very  soon  after  bringing  the  tropometer  to  its  present  state  of 
adaptability  to  its  purpose,  and  learning  something  of  the  peculiarities 
of  ocular  rotations  from  more  critical  methods  than  had  hitherto  been 
employed,  it  became  evident  that  certain  peculiarities  in  the  excursions 
of  the  eyes,  in  the  vertical  direction  especially,  were,  as  a  rule,  asso- 
ciated with  certain  types  of  the  cranium.  The  more  attention  was 
directed  to  these  coincidences  the  more  certain  did  it  appear  that 
there  was,  in  this  relation,  an  important  law  which  would  well  repay 
more  than  a  casual  thought. 

As  investigations  proceeded,  it  was  found  that  three  classes  of . 
ocular  conditions  were  in  close  relation  with  the  three  great  types  of 
crania  recognized  by  anthropologists  and  craniologists,  and  that  the 
facial  angles  also,  with  some  modification  from  the  usual  rules  of 
craniologic  measurements,  serve  as  indications  of  directions  of  the 
eyes  in  passive  adjustment  with  reference  to  the  horizon. 

In  order  to  obtain  a  clear  conception  of  this  law,  so  far  as  it  has 
been  developed,  some  knowledge  of  the  types  of  the  cranium  and  of 
some  of  the  angles  of  the  face  is  requisite. 


NORMAL  DIRECTIONS  OF  PLANES  OF  VISION,  205 

Craniologists  classify  skulls  as  dolichocephalic  (long  skulls), 
mesocephalic  (medium  skulls),  and  ~brachy  cephalic  (broad  skulls). 
The  diagrams  (Figs.  78,  79,  and  80)  give  a  general  outline  of  these 
forms  of  the  skull  when  looked  at  from  above. 

The  basis  for  the  classification  consists  of  the  proportion  which 
the  longest  diameter  from  before  backward  bears  to  the  longest  trans- 
verse diameter.  If  the  transverse  diameter  is  75/100  that  of  the  longer 
diameter  or  less  than  75/100>  the  head  is  said  to  be  in  the  class  of  long 
heads;  but  if  the  transverse  diameter  equals  or  exceeds  85/100  the 
length  of  the  skull,  it  is  a  broad  skull.  Medium  skulls,  or,  as  we  may 
call  them,  tall  skulls,  are  those  in  which  the  transverse  diameter  is 
between  75/100  and  S5A0o  °f  the  long  diameter,  and,  as  might  be  sup- 
posed, the  measurement  from  the  base  of  the  skull  to  its  summit,  while 


Fig.  78.— The  Long  Fig.  79.— The  Tall  Fig.  80.— The  Broad 

Head.  Head.  Head. 


it  may  not  of  itself  be  greater  in  an  individual  case  than  that  of  one 
of  the  long  or  one  of  the  broad  type,  nor  even  so  great,  is  greater  in 
proportion  to  the  other  measurements. 

In  typical  heads  belonging  to  any  one  of  these  types  the  out- 
line of  the  face  is  likely  to  be  characteristic  of  the  type.  Thus,  the 
general  outline  of  the  face  from  the  line  of  the  brows  to  the  tip  of 
the  chin  as  seen  from  the  side  differs,  as  a  rule,  according  to  the  type 
of  the  cranium.  Associated  with  the  long  cranium  there  is  generally 
a  convex  facial  outline,  while  a  side  view  of  the  face  of  one  from  the 
class  of  tall  heads  shows  usually  very  little  or  no  curve.  On  the  other 
hand,  the  face  of  one  from  the  class  of  broad  skulls  is  likely  to  show  a 
concave  line. 


206 


PHYSIOLOGY. 


The  next  series  of  figures  (81,  82,  83)  gives  an  idea  of  the  general 
form  from  a  side  view  of  each  of  these  three  types  in  the  living  subject. 


Fig.  81.— The  Long       Fig.  82.— The  Tall   (Medium)       Fig.  83.— The  Broad 
Head.  Head.  Head. 


Facial  Angle  +  10°. 


Facial  Angle  0°. 


Facial  Angle  — 10°. 


To  nearly  all  general  laws  affecting  the  form  of  the  human  body 
there  are  exceptions,  and  the  rule  just  stated  is  not  absolutely  uniform 
in  its  application.  However,  the  type  of  head  and  the  outline  of  face 


Fig.  84. — Broca's  Calipers. 


are  generally  in  the  relation  shown  by  the  diagrams,  and  the  general 
fact  may  be  thus  stated :   With  the  long  skull  the  angle  of  the  face  is 


NORMAL  DIRECTIONS  OF  PLANES  OF  VISION.  207 

high;  with  the  medium  or  tall  skull  there  is  a  low  angle  or  none, 
while  with  the  broad  skull  there  is  a  negative  facial  angle. 

By  referring  to  the  notes  below  the  figures,  it  will  be  seen  that 
the  upward  rotations  of  the  eyes  are  quite  different  in  these  cases,  and 
the  rotations  recorded  under  the  figures  fairly  represent  that  which 
may  be  expected  in  association  with  a  head  belonging  to  the  particular 
class,  while  there  may  be  individual  differences. 

The  transverse  and  longitudinal  diameters  of  the  head  are  deter- 
mined by  the  calipers  of  Broca  (Fig.  84),  and  the  angle  of  the  face 
by  the  facial  goniometer  which  1  have  devised  (Fig.  85).  In  using 
the  calipers  the  bulbs  are  placed  at  the  broadest  interparietal  diameter 


Fig.  85. — Author's  Facial  Goniometer. 

for  the  transverse  measurement,  and  on  the  glabella  in  front  and  at 
the  occipital  protruberance  behind  for  the  long  diameter.  In  deter- 
mining the  facial  angle  the  upper  foot  of  the  goniometer  is  placed 
at  the  glabella,  the  center  foot  at  the  depression  immediately  below  the 
nose  and  the  lower  foot  at  the  point  of  the  chin,  the  teeth  being  nat- 
urally closed. 

The  direction  of  the  normal  visual  plane  to  the  type  of  the  cra- 
nium in  each  of  the  three  classes  may  be  arrived  at  by  direct  and  by 
indirect  methods. 

In  the  case  of  the  living  subject,  the  dimensions  of  the  head  may 
be  taken  and  the  plane  of  vision  established  in  the  same  individual. 


208 


PHYSIOLOGY. 


The  determination  of  the  plane  of  vision  in  the  living  subject  is  ac- 
complished through  the  aid  of  the  tropometer.  The  relation  is  thus 
established  by  a  direct  method. 

The  indirect  method  is  that  of  ascertaining  the  direction  of  the 
imaginary  line  constituting  the  axis  of  the  orbit  in  the  prepared  skull, 
the  measurements  of  which  are  known.  The  orbits  are  more  or  less 
cone-shaped.  If  the  extreme  apex  of  the  cone,  at  which  the  optic  nerve 
enters  it,  is  taken  as  one  point  of  the  line  of  the  axis,  and  a  point  where 
two  straight  lines,  drawn  at  nearly  right  angles  with  each  other  from 
certain  parts  of  the  circle  of  bone  constituting  the  outer  border  of  the 
orbit,  cross  is  taken  as  another  point  in  the  line  of  the  axis,  the  line 
which  would  pass  through  these  two  points  would  represent  the  axis. 
This  imaginary  line,  if  projected  forward  and  beyond  the  orbit,  would 


Fig.  86. — The  Author's  Method  of  Determining  the  Axis  of  the  Orbit. 


be  seen  in  most  cases  to  point  somewhat  downward,  the  skull  being  in 
the  primary  position,  and  in  some  types  of  skulls  it  points  much  more 
downward  than  in  other  types. 

To  maintain  the  skull  in  the  correct  position  I  have  devised  the 
apparatus  shown  at  Fig.  86.  The  standard  in  front  carries  two  bulb- 
bearing  movable  bars.  One  of  these  bulbs,  the  upper,  is  in  contact 
with  the  glabella,  the  other  with  the  depression  below  the  nasal  spine. 
Thus  the  skull  is  in  a  position  corresponding  with  that  of  the  head 
when  the  rotations  are  being  determined  by  the  tropometer. 

It  is  interesting  to  find  that  the  pointing  of  the  imaginary  line 
representing  the  axis  of  the  orbit  closely  corresponds  with  the  ob- 
servations on  the  normal  visiial  plane  in  the  living  subject. 

The  interest  is  more  considerable  when  it  is  found  that  the  form 
of  the  orbit  in  the  different  classes  of  skulls  offers  an  explanation  of 


NORMAL  DIRECTIONS  OF  PLANES  OF  VISION. 


209 


the  peculiarities  in  the  direction  of  the  orbital  axis,  as  well  as  of  the 
normal  plane  of  vision. 

Figs.  87,  88,  and  89  represent  the  front  views  of  skulls  of  the 
long,  tall  and  broad  types  respectively,  showing  the  form  of  the  orbit 
corresponding  to  each  type.  It  will  be  seen  that  in  the  long  skull 
(Fig.  87)  the  roof  of  the  orbit  is  much  lower  than  that  of  the  tall 
skull  (Fig.  88),  and  that  the  lower  border  extends  more  downward. 
The  orbit  of  the  tall  skull  is  not  only  placed  with  its  opening  higher, 
but  it  is  more  narrow  from  side  to  side.  In  the  case  of  the  broad  skull 
(Fig.  89)  the  roof  of  the  orbit  is  low  like  that  of  the  long  skull,  but 
the  lower  border  does  not  extend  so  far  downward  and  the'  direction 
of  the  transverse  diameter  is  more  oblique. 

Measurements  of  the  direction  of  the  axis  of  the  orbit  in  these 
three  classes  show  that  in  the  long  skull  the  direction  is  usually  quite 


Fig.  87. 

Front  View  of  Long 
Skull: 


Fig.  88. 

Front  View  of  Tall 
Skull: 


Fig  89. 

Front  View  of  Broad 
Skull: 


low,  that  in  the  tall  skull  it  is  much  higher,  and  that,  while  the  axis 
of  the  broad  skull  is  lower  than  that  of  the  tall  one,  it  is  scarcely  as 
low  on  the  average  as  in  the  case  of  the  long  skull;  and  these  com- 
parative positions  of  the  axes  of  the  orbits  in  the  prepared  skulls  cor- 
respond remarkably  with  the  positions  of  the  visual  plane  in  the  case 
of  living  subjects  with  heads  of  corresponding  types.  That  is,  the 
visual  plane  of  the  long  head  is  low,  of  the  broad  head  also  low,  and 
that  of  the  tall  head  is  high. 

In  the  investigations  which  I  have  made  I  have  found  that  while 
in  mesocephalic  skulls  the  axis  of  the  orbit  sometimes  is  higher  than 
the  plane  of  the  horizon,  the  average  of  such  skulls  shows  a  slight 
depression.  This  depression  in  22  mesocephalic  skulls  amounts,  on 


210  PHYSIOLOGY. 

the  average,  to  about  3°.  In  dolichocephalic  skulls  (index  78°  and 
under)  the  axis  of  the  orbit  is  directed  below  the  plane  of  horizon  from 
5°  to  15°,  the  average  of  those  examined  by  me  being  7°  or  8°  of 
depression.  In  brachycephalic  skulls  the  orbital  axis  is  also  directed 
downward,  but  less,  on  the  average,  than  in  the  case  of  the  dolicho- 
cephalic. Here  the  depression  of  the  axis  ranges  in  general  from  4° 
to  12°,  averaging  6.5°.  In  two  cases  the  axis  has  been  elevated  above 
the  horizontal  plane,  but  in  these  the  head  was  very  high  in  propor- 
tion to  the  length. 

Notwithstanding  the  apparent  simplicity  of  these  relations  of  the 
form  of  the  orbit  with  the  type  of  the  skull  and  of  the  direction  of 
the  visual  plane  to  the  type  of  cranium,  there  are,  in  practice,  certain 
modifying  features,  principal  among  which  is  the  facial  angle  already 
referred  to. 

Taking  into  consideration  that  even  in  the  case  of  the  meso- 
cephalic  skull  the  average  orbital  axis  is  rather  below  the  horizon, 
and  considering  also  that  of  the  83°  of  rotation  only  33°  to  37°  are, 
in  the  best  condition,  above  the  horizon,  it  would  seem  that  the  most 
favorable  position  for  the  normal  visual  plane  would  not  be  exactly 
at  the  horizon,  but  slightly  below  it.  In  the  use  of  the  eyes  the  plane 
of  regard  is  generally  depressed  and  rarely  elevated. 

The  form  of  the  orbit  is  such  that  less  freedom  of  rotation  might 
be  expected  in  the  upward  field  than  in  the  downward.  Allowing  for 
this,  the  difference  is  so  considerable  as  to  suggest  a  plane  most  favor- 
able for  the  normal  visual  plane  somewhat  in  conformity  with  the 
direction  of  the  orbital  axis. 

Experiments  made  with  the  clinoscope  have  indicated  clearly 
that  the  visual  plane  cannot  be  more  than  about  3°  below  the  horizon, 
as  shown  by  the  restriction  of  upward  rotation  without  inducing  tor- 
sion; hence,  with  a  latitude  of  from  32°  to  37°  of  upward  rotation 
we  shall  find  the  normal  plane  of  vision  within  the  limits  of  the  best 
position. 

The  results  of  examinations,  commenced  in  1896  and  extending 
up  to  the  present  time,  and  including  a  great  number  of  cases,  may 
be  briefly  summarized  as  follows : — 

The  normal  plane  of  vision  is  rarely  coincident  with  the  horizon 
or  within  3°  below  it,  but  is  much  more  frequently  elevated  mate- 
rially above  it  or  depressed  materially  below  it.  In  a  large  majority 
of  cases  after  the  subject  of  the  examination  has  had  sufficient  prac- 
tice to  bring  the  elevator  and  depressor  muscles  fully  into  action,  the 


NORMAL  DIRECTIONS  OF  FLAXES  OF  VISION.  211 

upward  vertical  rotation  either  falls  below  30°  or  exceeds  37°.  There 
is  thus  an  interval  of  about  5°  to  7°  in  the  records  of  upward  rotation 
within  which  the  limit  of  excursion  is  more  rarely  found  than  above 
or  below  it. 

In  the  class  in  which  the  upward  rotation  exceeds  37°  it  is  most 
frequently  about  40°,  but  may  extend  to  50°,  or  even  more.  In  the 
class  in  which  the  upward  rotation  fails  to  reach  31°,  it  is  most  likely 
to  reach  from  28°  to  30°,  but  may  fall  as  low  as  15°  in  eyes  which 
are  normal  and  in  which  the  flexibility  of  youth  and  every  accessory 
condition  would  seem  favorable. 

These  facts  may  be  compared  with  the  remark  of  Benedikt1  that 
in  the  measurements  of  a  great  series  of  skulls  he  has  not  found  a  case 
of  orthagnathism  (one  in  which  the  facial  angle  is  0). 

In  mesocephalic  heads  with  a  very  low  facial  angle  (orthag- 
nathism) the  rotation  is  usually  high,  with  a  corresponding  restric- 
tion of  the  rotation  downward.  For  example,  if  the  upward  rotation 
is  40°,  the  downward  is  limited  to  40°,  or  perhaps  45°.  If  the  head 
is  quite  high  in  proportion  to  its  length,  the  upward  rotation  is  likely 
to  extend  in  proportion  to  the  index  of  height  of  the  cranium.  A 
glance  at  Fig.  88  will  help  to  understand  the  reason  for  this  excess 
of  rotation  upward  in  this  class  of  heads,  for  with  the  vault  of  the 
orbit  extending  upward  to  a  greater  extent  than  in  the  other  types  of 
the  skull,  there  is  space  for  this  movement  to  be  made  without  the 
restriction  which  exists  in  the  other  types.  But  since  the  lower  floor 
of  the  orbit  is  also  higher  in  this  type,  the  downward  rotation  is  of 
less  extent.  The  axis  of  the  orbit,  as  has  been  shown,  in  this  type  of 
skull  points  higher  than  in  any  of  the  types  and  the  normal  visual 
plane  is  higher  than  the  plane  of  the  horizon. 

In  long  heads,  especially  long  heads  with  a  high  positive  facial 
angle  (Fig.  80),  the  rotation  upward  nearly  always  comes  short  of  the 
standard  and  the  downward  rotation  exceeds  50°.  Again,  a  reference 
to  Fig.  87  shows  the  physical  limitation  of  the  upward  rotation  in  the 
low  vault  of  the  orbit  and  of  the  extended  rotation  down  in  the  lower 
plane  for  the  floor  of  the  cavity.  The  orbital  axis  points,  with  this 
type  of  skull,  lower  than  with  either  of  the  others.  The  plane  of 
vision  is  nearly  uniformly  below  the  horizon. 

A  glance  at  the  figure  of  the  broad  (brachy cephalic)  skull  will 
also  show  why  the  upward  rotation  of  this  type  of  head  is  restricted, 


'Benedikt:      "Kraniometrie  und  Kephalometrie."     Wien  und  Leipzig. 


212  PHYSIOLOGY. 

but  it  will  also  be  seen  that  with  this  restriction  upward  there  is  a 
limitation  downward,  for  the  lower  floor  of  the  orbit  approaches  much 
nearer  to  the  upper  than  it  does  in  the  long  skull,  and  is,  in  fact,  as 
high  as  that  of  the  mesocephalic  skull.  In  practice  it  is  found  that 
the  upward  rotation  of  a  person  with  this  type  of  head  is  usually  about 
or  less  than  30°,  while  the  downward  rotation  seldom  equals  40°. 

These  peculiarities  in  the  type  of  the  head,  and  consequently  in 
the  form  of  the  orbit,  have  a  very  practical  bearing  upon  the  adjust- 
ment of  the  eyes.  If  the  plane  of  vision  is  normally  situated  coin- 
cident with  the  horizon  when  the  head  is  in  the  primary  position  then 
(in  the  absence  of  other  anomalies)  with  every  adjustment  for  con- 
vergence with  depression  there  occur  the  torsions  exactly  according  to 
the  law  which  has  been  shown.  But  if  the  normal  plane  of  vision 
is  directed  above  the  horizon,  then  torsions  must  already  occur  before 
the  visual  plane  coincides  with  the  horizon,  and  when  depression  is 
effected,  the  torsions  are  excessive  and  the  horopter  is  not  formed. 
So  also  when  the  visual  plane  is  normally  depressed,  the  horopter  is 
not  formed  at  the  point  of  regard,  since  the  depression  demanded  of 
the  eyes  is  less  than  the  depression  of  the  line  of  regard  from  the 
horizon.  In  either  case  there  is  confusion,  which  must  be  corrected 
by  adjustments  which  are  not  automatic.  In  nearly  all  such  cases  the 
subject  of  the  condition  makes  a  compensating  adjustment  by  the 
head.  Thus,  if  the  visual  plane  is  normally  elevated  he  carries  the 
head  forward  so  as  to  depress  the  orbital  axis.  The  forehead  is  ad- 
vanced beyond  the  position  to  which  it  would  otherwise  come.  This- 
influences  the  habitual  pose  of  the  body  and  the  walk  of  such  a  person. 
On  the  other  hand,  if  the  plane  of  vision  is  depressed  normally,  the 
person  subject  to  the  condition  is  in  nearly  every  case  accustomed  to 
throw  the  head  back  from  the  most  natural  pose.  His  usual  bodily 
pose,  his  gait,  and  appearance  are  modified  by  the  direction  of  the 
orbital  axis. 

In  another  section  in  which  the  applications  of  the  principles  of 
these  special  ocular  adjustments  are  treated  (Section  XXX)  this 
question  of  the  horopter  in  its  relation  to  the  elevation  or  depression 
of  the  visual  planes  will  be  discussed  from  the  practical  point  of  view. 
It  is  sufficient  here  to  say  that  these  conditions  are  of  great  importance, 
and  without  a  knowledge  of  them  there  can  be  no  adequate  under- 
standing of  the  horopter  or  of  the  anomalies  of  the  eye  muscles. 

It  will  be  observed  that  more  importance  has  been  assigned  to  the 
rotations  in  the  vertical  than  in  the  lateral  direction.  A  careful  con- 


NORMAL  DIRECTIONS  OF  PLANES  OF  VISION.  213 

sideration  of  the  principles  discussed  in  the  previous  chapter  will 
account  for  this.  It  will  be  seen,  when  these  principles  are  recalled, 
that  with  a  greater  or  less  action  of  the  muscles  which  rotate  the  eyes 
from  side  to  side,  torsions  are  not  influenced,  while  even  a  moderate 
action  of  either  the  elevating  or  depressing  muscles  induces  torsions 
and  thereby  influences  the  position  of  the  horopter. 

This  most  important  principle  is  to  be  considered  in  all  investi- 
gations of  the  anomalous  actions  of  the  eye  muscles. 


PAET  III. 


ANOMALOUS  CONDITIONS  OF  THE  MOTOR  MUSCLES  OF 
THE  EYES  CONSISTENT  WITH  THE  PHYSIOLOGICAL 
STATE.  CLASSIFACTION  AND  EXPOSITION  OF  THE 

CLASSES. 

SECTION  XXV. 

SYNOPSIS  OF  THE  CLASSIFICATION. 

In  this  classification  will  be  included : — 

1.  The  relation  of  the  normal   visual   planes   to    the   cranium. 

2.  The  relation  of  the  vertical    meridians    to    the    cranium. 

3.  The  relation  of  the  visual    lines   to    each    other. 

4.  Spasmodic    affections    of    the    eye    muscles   from    functional 
causes. 

Class  I. — Relations  of  the  Normal  Plane  of  Vision  of  the  Individual 

to  the  Cranium.1 

The  head  being  exactly  in  the  primary  position,  the  normal  plane 
of  vision  may  be,  with  the  minimum  of  nervous  energy  directed  to 
the  adjusting  muscles  of  the  eyes,  located  in  a  plane  coincident  with 
the  plane  of  the  horizon  or  not  more  than  3°  to  5°  below  or  above 
it.  This  state  of  adjustment,  in  order  to  distinguish  it  from  the 
other  adjustments  of  this  class  and  from  orthophoria,  of  Class  III, 
may  be  called  euthyphoria. 

Of  this  first  class  there  are  five  kinds  of  adjustments. 

1.  EUTHYPHORIA. — A  passive  adjustment  of  the  normal  plane 


1  The  description  of  the  conditions  of  this  class  and  the  terminology  were 
first  published  in  Annales  d'Oculistique,  April,  1894,  from  proceedings  of  British 
Medical  Association,  1893. 

(214) 


CLASSIFICATION.  215 

of  vision  such  that  this  visual  plane  is  coincident  with  the  plane  of 
the  horizon,  or  very  nearly  so. 

2.  ANOPHORIA. — A    passive    adjustment   of    the   normal   visual 
plane  at  an  angle  distinctly  above  the  plane  of  the  horizon. 

3.  KATOPHORIA. — A  passive  adjustment  of  the  visual  plane  at 
an  angle  distinctly  below  the  plane  of  the  horizon. 

4.  ANOTROPIA. — An  adjustment  in  which  the  visual  line  of  either 
eye  deviates  upward  when  the  other  is  in  fixation. 

5.  KATOTROPIA. — An  adjustment  in  which  the  visual   line   of 
either  eye  deviates  downward  when  the  other  is  in  fixation. 

Class  II. — Declinations  of  the  Retinal  Meridians. 

RELATIONS   OF  THE  VISUAL  LINES   OF  THE  TWO  EYES  TO 
EACH  OTHER. 

Class  III. 
FIRST  Divisioisr.1 

Adjustment  of  the  Directing  Muscles  of  the  Two  Eyes  by  Which  the 
Two  Visual  Lines  May  Be  and  Are  so  Related  that  Binocular  Vision 
is  Habitually  Maintained. 

The  generic  divisions  of  this  class  are: — 

1.  ORTHOPHORIA    (6p06s ,  right;    <f>opd,  a    tending). — A     tend- 
ing of  the  visual  lines  in  parallelism,  the  determination  being  made 
for  a  point  not  less  than  6  meters  distant. 

2.  HETEROPHORIA    (erepos,  different). — A      tending     of     these 
lines  in  some  other  way,  the  determination  being  made  for  a  distant 
point,  as  above  indicated. 

The  specific  conditions  of  heterophoria  are: — 

1.  Esophoria. — A  tending  of  the  visual  lines  inward  (or  toward 
each  other). 

2.  Exophoria. — A  tending  of  the  visual  lines  outward  (or  away 
from  each  other). 

3.  Tlyperphoria.  (right  or  left). — A  tending  of  the  right  or  of 
the  left  visual  line  in  a  direction  above  its  fellow. 


1  The  classification  and  terminology  of  this  Division  were"  first  published 
in  Archives  d'Ophthalmologie,  November,  1886;  New  York  Medical  Journal, 
December  4,  1886. 


216  ANOMALIES  OF  MOTOR  MUSCLES. 

This  term  docs  not  imply  that  the  line  to  which  it  is  referred  is 
too  high,  but  that  it  is  higher  than  the  other,  without  indicating  which 
may  lie  at  fault.1 

Tendencies  in  oblique  directions  are  expressed  as: — 

4.  Hyperesophoria. — A   tendency   of   one   visual   line   above   the 
other  with  a  tendency  of  the  lines  inward. 

5.  Hyperexophoria. — A  tendency  of  one  visual  line  above  the 
other  with  a  tendency  of  the  lines  outward.    The  designation  "right" 
or  "left"  must  be  applied  to  these  compound  terms. 

Class  III. 

SECOND  DIVISION. 

Adjustments  by  which  Binocular  Vision  is  not  Habitually  Maintained. 

HETEROTROPIA  (Tp«mv,  to  turn). — Deviations  of  the  visual  lines 
consistent  with  a  physiological  state  of  the  motor  muscles  and  nerves. 

This  class  includes  anomalous  conditions  in  which,  the  visual  line 
of  one  eye  being  directed  to  the  distant  point  as  above  indicated,  and, 
in  general,  to  any  point  in  the  field  of  regard,  the  visual  line  of  the 
other  eye  is  directed  to  some  other  point. 

The  specific  divisions  in  this  class  are: — 

1.  Esotropia. — A  deviation  of  the  visual  lines  inward. 

2.  Exotropia. — A  deviation  of  the  visual  lines  outward. 

3.  Hypertropia  (right  or  left). — A  deviation  of  one  visual  line 
above  the  other. 

4.  Hyperesotropia. — A  deviation  of  one  visual  line  inward  and 
above  the  other. 

5.  Hyperexotropia. — A  deviation  of  one  visual  line  out  and  above 
the  other. 

When  these  conditions  exist  associated  with  the  usual  physio- 
logical state  of  the  eye  muscles  the  terms  which  have  been  in  common 
use  are,  for  heterotropia,  concomitant  strabismus;  for  esotropia,  con- 
verging concomitant  strabismus ;  for  exotropia,  diverging  concomi- 


1  Hence  there  can  be  no  necessity  for  a  term  to  indicate  that  one  line  is 
lower  than  the  other,  since  that  follows  as  a  matter  of  course.  The  attempts 
to  force  a  redundant  term  in  this  connection  indicate  a  confusion  of  mind 
in  respect  to  the  meaning  of  the  term  hyperphoria. 


CLASSIFICATION.  217 

tant  strabismus,  and  for  hypertropia,  strabismus  sursumvergens,  or 
strabismus  deorsumvergens.  For  the  compound  conditions  no  spe- 
cific terms  have  been  used. 

Class  IV. — Spasmodic  Affections  from  Functional  Causes. 
NYSTAGMUS. 


SECTION  XXYI. 

EXPOSITION  OF  THE  CLASSES. 

Class  I. — Relations  of  the  Normal  Plane  of  Vision  of  the  Individual 

to  the  Cranium. 

ANOPHORIA  AND  KATOPHORiA.1 

(This  section  should  be  read  in  connection  with  Section 
XXIY.) 

In  the  preceding  part  of  this  work  it  has  been  shown  that  the 
relations  of  the  normal  plane  of  vision  to  the  cranium  constitute 
important  factors  in  the  associated  use  of  the  eyes. 

It  has  been  stated  that  with  a  person  having  a  rotation  of  the 
eyes  from  the  horizontal  plane  upward  of  from  32°  to  37°  and  a 
downward  rotation  of  50°,  the  head  being  in  the  primary  position, 
the  plane  of  the  least  torsional  effect  is  at  the  horizon.  A  person  of 
quick  perceptions  and  who  is  practiced  with  the  clinoscope  having 
these  rotations  may,  if  the  clinoscope  is  pointed  exactly  in  the  plane 
of  the  horizon,  find  a  certain  degree  of  leaning  of  the  vertical  meri- 
dian of  one  of  his  eyes  or  of  each  of  them.  Taking  note  of  this, 
which  after  a  number  of  examinations  he  will  consider  his  personal 
pecularity  (declination),  he  will  find  that  by  changing  the  direction 
of  the  tubes  of  the  clinoscope  this  permanent  factor  is  modified.  Let 
us  now  suppose  that  the  person  with  the  rotations  mentioned  finds, 
declination,  E.  +  1°,  L.  0°.  If  the  tubes  are  directed  upward  from 
the  horizon  5°  the  leaning  of  the  meridians  outward  will  increase, 


1  Stevens:     Annales  d'Oculistique,  April,  1894;    a  paper  read  before  the 
British  Medical  Association  at  its  session,  1893. 


218  ANOMALIES  OF  MOTOR  MUSCLES. 

bringing  the  decimation  to  perhaps  R.  -f-l1^0^  L.  -f-  ^4°.  If  he 
now  causes  the  tubes  of  the  instrument  to  point  down  (the  head  being 
always  in  the  primary  position)  the  leanings  out  will  again  increase. 
Thus,  the  minimum  leaning  of  the  meridians  for  this  person  will  be 
practically  at  the  horizon. 

If  a  person  with  a  greater  upward  rotation,  say  of  40°,  after 
having  carefully  determined  the  leanings  of  the  meridians  at  the 
horizon,  points  the  instrument  up  5°,  the  outward  leanings,  if  there 
are  any,  will  decrease.  But  if  the  tubes  are  made  to  point  up  again 
5°,  that  is,  in  all  10°,  the  leanings  out  will  again  increase.  Thus, 
for  a  person  with  this  rotation  the  plane  of  least  deviation  of  the 
meridians  is  not  at  the  horizon  but  above  it. 

When  the  normal  plane  of  vision  is  at  the  horizon  no  torsion 
occurs  in  that  plane.1  When  the  normal  plane  of  vision  is  above  the 
horizon  there  is  torsion  in  the  horizontal  plane,  but  none  in  a  certain 
plane  above.  In  like  manner  if  the  normal  plane  of  vision  is  below 
the  horizon  then  the  plane  of  least  leaning  out  of  the  meridians  of 
the  eye  is  below  the  plane  of  the  horizon. 

By  facts  of  this  kind  it  has  been  found  that  with  a  rotation  of 
the  eyes  up  from  the  horizon  from  32°  to  36°  or  37°,  and  with  a 
downward  rotation  of  from  45°  to  50°,  the  plane  of  normal  vision 
for  the  individual  is  practically  at  the  horizon.  If  the  upward  rota- 
tion materially  exceeds  this  the  normal  plane  of  vision  is  above  the 
horizon,  and,  if  it  is  materially  less,  this  plane  is  below  the  horizon. 

It  is  thus  seen  that  as  a  result  of  various  positions  of  the  plane 
of  vision  horopters  are  not  uniformly  formed  for  different  persons, 
and  experience  shows  that  the  most  favorable  position  for  the  normal 
plane  of  vision  is  at  the  horizon. 

It  is  now  known  that  anomalous  muscular  conditions  which  have 
been  supposed  to  be  quite  independent  of  any  influences  outside  the 
muscles  apparently  directly  affected  or  of  the  nerves  controlling  these 
muscles  are,  in  fact,  not  unfrequently  manifestations  of  unfavorable 
relations  of  the  normal  plane  of  vision  to  the  cranium.2 

Only  a  small  proportion  of  persons  appear  to  have  the  normal 


JThe  word  torsion  must  not  be  confounded  with  declination,  which  is 
another  condition. 

2  The  important  fact  that  when  the  normal  visual  plane  does  not  coincide 
with  the  horizon  disturbances  of  the  harmonious  actions  of  the  muscles  govern- 


EXPOSITION  OF  CLASSES.  219 

visual  plane  exactly  at  the  horizon.  In  this  respect  examinations  by 
the  tropometer  and  clinoscope  appear  to  be  in  harmony  with  the 
observations  of  craniologists. 


ANOPHORIA. 

Referring  to  Section  XXIV  it  will  be  seen  how,  with  the  type 
of  cranium,  the  axis  of  the  orbit  varies,  forming  an  angle  with  the 
horizon,  sometimes  rising  above  that  plane  and  sometimes  falling 
below  it.  The  extent  of  the  rotations  of  the  eyes  in  the  vertical 
directions  are,  to  a  remarkable  extent,  in  harmony  with  the  cranial 
type.  If  the  type  of  head  is  that  known  as  mesocephalic,  and  espe- 
cially if  the  line  of  the  face  is  that  of  orthagnathism,  the  rotations 
are  so  generally  high  that  it  may  be  regarded  as  a  rule  that  with  such 
a  type  of  cranium  there  will  be  found  the  condition  of  anophoria. 

Anophoria  does  not  indicate  a  weakness  of  any  set  of  muscles 
nor  any  overaction  of  any  set.  It  is  an  adjustment  coincident  to  the 
type  of  the  head. 

It  may  be  sugested  that  a  condition  normal  to  the  great  class 
of  people  who  have  this  type  of  head  should  be  favorable  to  that  type : 
that  in  the  process  of  evolution,  if  that  is  the  process  to  which  the 
variations  of  cranial  types  are  due,  the  adjustments  of  the  eyes  would 
conform  to  the  most  favorable  plane  as  the  evolutionary  process  pro- 
ceeded. 

This  and  other  like  suggestions  may  be  met  by  the  statement  that 
practical  experience  does  not  confirm  the  view  that  anophoria,  while 
it  is  normal  to  the  average  mesocephalic  head,  is  a  favorable  adjust- 
ment of  the  eyes. 

When  entirely  simple,  when  it  is  complicated  by  neither  hyper- 
phoria  nor  esophoria,  and  especially  when  it  is  not  accompanied  by 
a  considerable  degree  of  declination,  it  may  cause  little  if  any  incon- 
venience, especially  if  it  occurs  in  a  person  of  vigorous  constitution. 
Even  with  all  these  favoring  circumstances,  it  may  prove  an  element 


ing  the  movements  of  the  eyes  may  be  induced  by  such  adjustments,  was  first 
pointed  out  by  me  in  1894,  in  a  paper  read  at  the  meeting  of  the  British 
Medical  Association,  and  later,  in  another  paper  read  at  the  International 
Ophthalmological  Congress  at  Edinburgh,  August  10th,  in  the  same  year. 
The  first  of  these  papers  was  published  in  Annales  d'Oculistique,  April  and 
June,  1895,  the  other  in  the  proceedings.  Also  in  New  York  Medical  Journal, 
February  16,  1895. 


ANOMALIES  OF  MOTOR  MUSCLES. 

of  fatigue,  local  and  general,  it  may  affect  the  carriage  of  the  indi- 
vidual quite  unfavorably  to  the  best  interests  of  health,  and  it  may 
induce  general  disturbance  of  the  nervous  functions. 

Some  of  the  more  obvious  indications  of  anophoria  are  readily 
recognized  by  the  experienced  observer  in  the  facial  expressions  and 
in  the  bodily  pose  of  the  person  subject  of  the  condition. 

So  intimately,  however,  are  the  physical  causes  now  under  con- 
sideration and  which  induce  these  facial  expressions  and  bodily  poses 
associated  with  the  phenomena  of  declinations  which  are  to  be  dis- 
cussed in  the  succeeding  section,  that  it  is  difficult  if  not  impossible 
to  consider  such  expressions  and  poses  from  either  standpoint  sepa- 
rately. In  nearly  all  of  the  more  or  less  extreme  cases  of  anophoria 
will  be  found  also  important  degrees  of  declination,  and  these  combine 
to  give  character  to  the  tensions  of  the  facial  muscles,  as  they  do  also 
to  the  muscles  which  influence  the  bodily  pose. 

In  respect  also  to  the  physical  effects,  the  heterophoria,  the 
nervous  disturbances,  the  respiratory  restrictions  and  other  results 
of  anophoria,  these  conditions  of  declinations  become  modifying  fac- 
tors of  an  important  nature,  sometimes  intensifying  the  effects  of  the 
anophoria  and  sometimes,  in  a  measure,  neutralizing  these  effects.  It 
is  therefore,  in  practice,  impossible,  in  discussion,  to  separate  these 
two  classes  of  conditions,  both  dependent  on  peculiarities  in  the 
construction  of  the  orbits. 

It  must  then  be  permitted  that  in  discussing  the  subject  of  ano- 
phoria and  katophoria,  some  things  shall  be  anticipated  which  are 
not  yet  reached  in  the  regular  order  of  our  classification  and  in  the 
development  of  our  subject. 

Eeturning  to  the  statement  that  some  of  the  more  obvious  in- 
dications of  anophoria  are  recognized  in  the  facial  expressions  and  in 
the  bodily  pose  of  the  individual,  one  or  two  of  the  most  characteristic 
of  these  may  be  here  mentioned. 

Anophoria,  uncomplicated,  induces  a  strong  pressure  of  the  brows 
downward.  The  line  of  each  brow  only  slightly,  if  at  all,  arched  is 
crowded  down  to  the  border  of  the  orbit  and  against  the  upper  part 
of  the  eyelids.  The  lids  do  not  open  widely,  but  show  a  narrow  pal- 
pebral  space. 

A  strong  positive  declination  in  each  eye  may  so  modify  this  as 
to  elevate  both  brows,  while  a  very  decided  positive  declination  for 
one  eye  and  negative  one  for  the  other  eye  may  elevate  one  brow  and 


EXPOSITION  OF  CLASSES.  221 

force  the  other  even  to  a  greater  compression  than  would  the  uncom- 
plicated anophoria. 

In  pose  of  body  the  characteristics  are  marked.  Uncomplicated, 
the  head  is  thrown  forward.  The  chin  approaches  the  chest.  The 
capacity  of  the  chest  is  restricted  and  its  full  expansion  hindered, 
and  the  respiration  is  often  impeded  by  a  partial  closing  of  the  air 
passages  in  the  vicinity  of  the  larynx.  Positive  declination  of  both 
eyes  may  raise  the  head  to  some  extent,  and,  even  when  of  very  high 
degree,  may  give  it  the  pose  which  we  shall  find  most  characteristic 
of  katophoria,  and  homonymous  declinations  of  high  degree  may 
throw  the  head  to  one  side.  As  a  rule,  however,  the  head  is  thrown 
forward  and  the  chest  may  be  compressed. 

From  the  facts  above  stated  it  may  be  seen  that  persons  with  this 
peculiar  adjustment  of  the  eyes  must  be  more  easily  predisposed  to 
phthisis  than  those  whose  normal  visual  plane  is  less  elevated.  The 
form  of  the  head,  including  that  of  the  orbits,  is  hereditary.  The 
doctrine  that  phthisis  is  transmitted  by  inheritance  has,  during  the 
past  few  years,  materially  lost  ground,  as,  when  it  is  considered  that 
the  essential  element  of  the  disease  is  the  tubercular  bacillus,  it  nat- 
urally would.  But  the  fact  remains  that  phthisis  runs  in  families. 
When  it  is  recalled  that  the  shape  of  the  bony  walls  of  the  orbits  is 
inherited,  and  that,  resulting  from  the  peculiarities  we  have  been 
considering,  the  respiratory  act  is  less  free  than  it  should  be,  is  it  not 
easy  to  understand  that  this  class  of  persons  are  in  a  physical  state  to 
invite  the  bacillus  and  that,  from  the  mechanics  of  the  respiratory 
tract,  the  earliest  home  of  the  germs  would  be  in  the  upper  parts  of 
that  tract? 

Even  when  this  bacillus  fails  to  find  lodgment,  the  restricted  res- 
piration is  an  important  factor  in  modifying  the  physical  condition; 
for  since  the  blood  is  less  completely  aerated,  there  may  be  less  of 
the  anabolic  process  of  nutrition,  and  even  a  process  of  katabolism 
may  be  induced.  Fortunately,  the  condition  of  anophoria  is  most 
frequently  found  in  a  class  of  persons  with  large  cranial  capacity. 
When  environments  and  circumstances  are  favorable,  the  large  nerve 
centers  may  control  the  nutritive  processes  to  such  an  extent  as  to 
render  them  abundantly  sufficient.  Under  more  adverse  circum- 
stances katabolism  may  result. 


222  ANOMALIES  OF  MOTOR  MUSCLES. 

KATOPHORIA. 

The  eyes  fail,  in  katophoria,  to  rotate  upward  to  the  extent  which 
would  indicate  euthyphoria.  It  has  been  seen  that  with  an  excessive 
rotation  up  there  is  slight  rolling  outward  of  the  vertical  meridians 
of  the  eyes  when  the  plane  of  regard  is  at  the  horizon,  and  that  this 
rolling  out  decreases  as  the  plane  of  regard  is  elevated  up  to  a  certain 
point,  beyond  which  it  again  increases. 

With  katophoria,  the  plane  of  least  rolling  out  of  the  meridians 
is  below  the  horizon. 

If  the  upward  rotation  of  the  eyes,  for  example,  is  28°  each,  the 
leaning  of  the  meridians  is  greater  when  the  p:ane  of  regard  is  at 
the  horizon  than  when  it  is  at  5°  below  it.  Beyond  this  5°  of 
depression  the  leaning  again  increases.  The  result  is  the  same 
whether  the  tubes  of  the  clinoscope  are  depressed  or  the  chin  of  the 
person  examined  is  thrust  forward  to  give  the  facial  line  an  equal 
recession.  It  is  this  class  of  facts  that  leads  to  the  conclusion  that  the 
normal  plane  of  vision,  when  best  placed  for  conforming  to  all  of 
the  conditions  involved  in  the  Law  of  Listing,  is  that  which  is  asso- 
ciated with  an  upward  rotation  of  the  eyes  of  from  33°  to  37°. 

Different  cases  of  katophoria  do  not  all  show  a  uniform  down- 
ward rotation  compared  to  the  upward.  As  it  has  been  shown  in 
Section  XXIV,  the  downward  rotation  is  usually  greater  when  com- 
pared with  the  upward  in  heads  of  the  dolichocephalic  type  than  in 
those  of  the  brachycephalic.  And  this  difference  is  explained  by  the 
difference  in  the  conformation  of  the  orbit  in  the  two  classes.  There 
are  brachycephalic  heads  in  which  the  upward  rotations  are  even 
greater  than  of  the  mesocephalic,  but  this  is  not  the  general  rule. 

It  follows  that  while  the  rotations  are  nearly  equal  in  the  whole 
vertical  range  in  mesocephalic  and  dolichocephalic  heads,  being  about 
83°,  they  are  less  extensive  in  the  average  brachycephalic  head. 

The  expression  of  the  face  and  the  bodily  pose  are  quite  in  con- 
trast with  those  which  are  characteristic  of  the  uncomplicated  case 
of  anophoria. 

In  this  class,  unless  the  effect  is  neutralized  by  certain  declina- 
tions, the  brows  are  drawn  up,  the  lines  of  the  face  are  elongated  ver- 
tically, the  upper  lip  is  elongated  and  the  head  is  thrown  back  so 
that  the  chin  is  advanced  and  the  forehead  recedes  when  the  indi- 
vidual walks  or  when  he  sits  and  looks  considerably  in  advance.  The 
body  is  often  bent  backward  with  the  chest  protruding. 


EXPOSITION  OF  CLASSES.  223 

It  is  easy  to  see  that  if  the  chest  is  restricted  and  the  respiratory 
passages  partly  shut  in  a  valve-like  fashion  in  the  former  class,  there 
is  in  this  class  no  such  restriction,  either  in  the  capacity  of  the  chest 
or  in  the  freedom  of  the  air  passages.  It  may  not  be  impossible  for 
people  of  this  class  to  acquire  phthisis,  but  as  a  matter  of  fact  they 
rarely  do.  But  the  pains  in  the  back  of  the  neck,  in  the  middle  dorsal 
region,  and  even  in  the  lumbar  region  are  often  the  physical  protest 
against  the  tension  upon  the  muscles  of  these  parts. 

This  work  is  not  intended  as  a  treatise  on  general  diseases,  but 
these  references  to  a  subject  of  infinite  importance  seem  not  out  of 
place  in  this  connection. 

The  effect  of  katophoria  in  inducing  asthenopic  affections  is, 
like  that  of  anophoria,  very  considerable,  for  since  the  horoptors  are 
in  neither  case  located  at  the  points  of  convergence  of  the  lines  in 
depression,  the  perplexities  which  follow  the  use  of  the  eyes  may  give 
rise  to  asthenopic  symptoms  of  very  troublesome  character. 

However  much  the  conditions,  anophoria  and  katophoria,  may 
demand  of  increased  muscular  tension  in  making  the  necessary  ad- 
justments of  the  eyes  for  the  different  planes  of  regard,  it  may  well 
be  supposed  that  by  far  the  greater  excess  of  demands  upon  the  nerv- 
ous forces  arise  from  this  disturbance  in  the  location  of  the  horopters 
and  the  consequent  maladjustments  such  as  hyperphoria,  esophoria, 
etc.,  which  arise  from  these  disturbances. 

AXOTROPIA — KATOTROPIA. 

In  a  paper  read  at  the  meeting  of  the  British  Medical  Associa- 
tion in  1894,  I  described  a  class  of  strabismus  deviations,  not  before 
recognized,  as  double  vertical  strabismus.  The  two  forms  of  this  class 
of  squint  I  defined  in  Annales  d'Oculistique,  April,  1895,  as: — 

1.  Anotropla. — A  deviation  of  the  visual  line  of  either  eye  up- 
ward when  the  other  eye  is  in  fixation. 

2.  Katotropia. — A  deviation  of  the  visual  line  of  either  eye  down- 
ward when  the  other  is  in  fixation. 

In  this  class  of  squint,  if  either  eye  is  in  exclusion  while  the 
other  is  in  fixation,  the  excluded  eye  deviates  upward  or  downward 
according  to  the  form  of  the  strabismus.  Thus,  in  a  case  of  ano- 
tropia,  if  the  patient  directs  the  gaze  toward  a  distant  object  directly 
in  front  and  at  the  level  of  the  eyes,  if  a  visiting  card  is  slipped  in  front 
of  the  right  eye,  the  left  eye  will  fix  the  object  while  the  right  will 


224  ANOMALIES  OF  MOTOR  MUSCLES. 

rise,  in  some  cases,  several  millimeters.  Then,  changing  the  card  to 
the  left  eye,  the  right  comes  into  fixation  while  the  left  rises  in  the 
same  way  that  the  right  did  at  first.  The  extent  of  these  deviations  is 
sometimes  as  much  as  one-half  the  diameter  of  the  cornea.  In  kato- 
tropia,  whichever  eye  is  excluded  is  depressed. 

These  cases  often  present  the  complication  of  an  inward  or  out- 
ward squint. 

In  a  continuation  of  the  article  referred  to,  it  was  shown  that 
by  tenotomies  of  the  superior  muscles  the  lateral  squint  disappeared. 

Further  study  of  these  cases  leads  to  the  conclusion  that,  while 
in  these  cases  there  is  very  generally  a  marked  excess  of  upward 
rotation  in  the  anotropia  cases  and  failure  to  rotate  up,  with  ex- 
cessive rotation  down,  in  the  others,  there  is  yet  another  element  which 
is  essential  in  all  these  cases  and  one  which  was  not  at  that  time 
(1894)  fully  recognized.  This  is  a  declination  of  the  meridians  of 
the  eye  so  pronounced  that  it  may  be  easily  seen  by  the  observer  as 
the  eye  moves  up  or  down  for  fixation.  In  explanation  of  the  phe- 
nomenon of  each  eye  deviating  I  have  become  convinced  that  we  are 
to  look  to  the  declination ;  for  when,  by  tenotomy,  the  upward  rota- 
tion of  anotropic  eyes  has  been  reduced  to  the  standard  of  33°,  the 
eyes  will  still  squint  upward  in  exclusion.  On  the  other  hand,  if  the 
extreme  declination  is  materially  reduced,  the  upward  deviation 
ceases.  We  may  regard  the  deviation  as  synergic.  With  the  adjust- 
ment of  the  fixing  eye  to  correct  an  extreme  declination,  the  forcible 
action  of  the  superior  oblique  may  be  demanded.  With  this  strong 
action  the  fixing  eye  is  depressed,  but  to  counteract  the  depression, 
in  order  to  effect  fixation  at  the  horizon,  the  superior  rectus  comes 
strongly  into  action.  Simultaneously  and  synergically  with  this, 
the  superior  rectus  of  the  excluded  eye  acts,  but  since  there  is  no 
occasion  for  the  depressing  action  of  the  oblique,  that  eye  is  raised. 

This  subject  of  synergic  or  correlative  action  will  be  more  fully 
discussed  in  the  sections  on  the  lateral  forms  of  strabismus. 


DETERMINATION  OF  ROTATIONS.  225 

SECTION  XXVII. 

DETERMINATION  OF  THE  EXTENT  OF  THE  ROTATIONS  OF  THE  EYES. 

Previous  to  the  introduction  of  the  tropometer  there  was  no 
adequate  means  for  arriving  at  even  approximate  measurements  of  all 
the  rotations  of  the  eyes. 

The  employment  of  perimeters  for  this  purpose  naturally  led  to 
imperfect  results.  The  brow  above,  the  cheek  below,  and  the  nose  at 
the  medial  position  each  presented  an  obstacle  to  a  complete  measure- 
ment except  where  these  parts  were  unusual  in  conformation.  When 
distinguished  authorities  reported  that  by  the  aid  of  the  perimeter 
they  had  found  their  own  eyes  to  rotate  medianward  50°,  they  forgot 
that  it  would  have  been  physically  impossible  for  them  to  have  seen 
by  direct  vision  the  test  object  when  it  was  carried  in  this  direction 
nearly  to  that  extent.  So  also  the  upward  and  downward  rotations 
were  reported  as  having  been  determined  by  this  means  to  extents 
which  would  be  out  of  the  question  by  direct  vision. 

Hence  the  figures  representing  these  rotations  which  had  been 
endorsed  by  distinguished  names  were  not  only  unreliable,  but  posi- 
tively misleading. 

THE    TROPOMETER.1 

The  tropometer  is  designed  to  measure  the  various  rotations  of 
the  eyes  about  the  point  known  as  the  "center  of  rotation." 

Such  measurements  can  be  determined  in  every  direction,  up, 
down,  right,  left,  and  in  oblique  directions. 

From  what  has  gone  before  it  is  evident  that  in  distinct  vari- 
ance from  the  formerly  prevailing  thought,  the  questions  of  rotations 
in  the  vertical  directions  are  by  far  of  greatest  importance  in  prac- 
tice. 

The  instrument  consists  of  a  telescope  mounted  on  a  platform, 
at  the  opposite  end  of  which  is  a  head-rest.  The  telescope  may  be 
made  to  approach  or  to  recede  from  the  head-rest,  and  it  can  be 
raised  or  lowered.  It  rests  horizontally  on  a  movable  plate,  and  its 
objective  extremity  may  be  brought  directly  in  front  of  either  eye. 


1  The  tropometer  was  first  exhibited  and  described  at  the  meeting  of  the 
American  Medical  Association  at  Baltimore,  1894. 


226 


ANOMALIES  OF  MOTOR  MUSCLES. 


The  telescope  has  at  the  objective  end  a  prism  of  45°,  or  a  mir- 
ror placed  so  as  to  reflect  at  right  angles.  By  means  of  a  focusing 
lens  in  the  tube  the  image  of  the  eye  can  be  made  to  be  clearly  denned 
at  the  scale  in  the  eye-piece,  while  by  another  focusing  device  the  scale 
may  be  seen  clearly.  This  scale  is  represented  at  Fig.  91,  where  the 
lines  at  the  right  of  the  long  vertical  line  are  intended  to  indicate 
the  rotations  down,  those  at  the  left  the  rotations  up.  These  hori- 
zontal lines  are  arranged  to  indicate  upon  a  flat  surface  the  change 
of  position  of  a  point  on  a  spherical  body,  as  the  sphere  rotates  up 
or  down. 


Fig.  90. — Stevens's  Tropometer. 

Giving  the  scale  a  half  rotation,  the  horizontal  lines  become  ver- 
tical and  the  long  vertical  line  becomes  horizontal.  Then,  the  upper 
scale  measures  the  excursion  of  the  right  eye  out,  the  lower  its  rota- 
tion in.  The  lower  scale  measures  the  excursion  of  the  left  eye  out 
and  the  upper  its  rotation  in. 

The  head-rest,  which  is  designed  to  hold  the  head  exactly  in 
the  primary  position,  is  furnished  with  certain  accessories.  They  are, 
an  exchangeable  wooden  tooth-rest,  to  be  used  but  once  and  then 
destroyed.  It  slips  into  a  bronze  stirrup,  which  is  movable  up  and 
down,  forward  and  back.  There  is  also  a  pair  of  button  indicators, 
also  movable,  for  exactly  determining  the  primary  position.  The 
two  buttons  are  exactly  vertical  to  each  other. 


THE  TROPOMETER. 


227 


EXAMINATION  BY  THE  TROPOMETER. 

The  person,  the  rotation  of  whose  eyes  is  to  be  examined,  seizes 
the  strip  of  wood  between  the  teeth,  the  forehead  being  caused  to  press 
against  the  arc  of  the  head-rest  and  the  face  so  adjusted  that  the  two 
buttons  press,  the  upper  firmly  against  the  elevation  of  bone  which 
is  found  between  the  two  superciliary  ridges  (the  glabella),  the  lower 
against  the  upper  lip  by  firm  pressure  at  the  depression  of  the  upper 
jaw  just  below  the  nose  and  above  the  roots  of  the  teeth.  Both  but- 


Fig.  91.— The  Tropometer  Scale. 

tons  must  be  in  the  median  sagittal  plane.  The  head  thus  brought 
into  position,  it  is  to  be  made  secure  by  the  hand  of  the  examiner, 
the  thumb  against  the  arc  of  the  head-rest,  the  fingers  at  the  back  of 
the  head,  or  by  the  device  shown  in  the  figure.  The  hand  is  most 
serviceable,  since  the  examiner  can  by  it  detect  even  a  very  slight 
movement  of  the  head. 

The  head  being  thus  secured  in  position,  the  telescope  is  brought 
to  the  proper  height  and  a  focus  upon  the  cornea  is  arranged.  The 
telescope  should  stand  at  such  a  distance  from  the  eye  that  the  cornea 
exactly  fills  the  space  between  the  heavy  lines  of  the  scale.  (Fig.  91). 
This  can  be  best  accomplished  by  first  turning  the  scale  so  that  its 


228  ANOMALIES  OF  MOTOR  MUSCLES. 

main  lines  run  vertically,  Avhen  it  will  be  easy  to  adjust  for  the  hori- 
zontal diameter  of  the  cornea.  As  the  horizontal  and  vertical  diam- 
eters of  the  cornea  are  not  always  equal,  the  slight  difference  can  be 
adjusted  by  a  movement  of  the  standard.  The  examined  person 
directs  the  regard  exactly  at  the  center  of  the  circular  opening  of  the 
telescope.  (If  there  is  squint,  the  eye  not  under  examination  should 
be  covered.) 

If  it  is  proposed  first  to  examine  the  rotation  of  the  eye  upward,1 
the  scale  is  turned  to  permit  the  lines  to  run  horizontally.  The  op- 
erator, with  the  thumb  of  the  left  hand  on  the  upright  branch  of 
the  head-rest  and  the  fingers  of  that  hand  pressed  firmly  against  the 
back  of  the  head  of  the  observed,  both  for  the  prevention  of  any 
movement  and  for  its  detection  if  it  occurs,  uses  the  tip  of  the  index 
finger  of  the  right  hand  to  depress  very  slightly  the  lower  lid  of  the 
eye  to  be  examined. 

The  lower  (apparently  upper)  strong  line  of  the  scale  is  then, 
by  means  of  the  lifting  screw  at  the  side  of  the  upright  standard, 
made  to  coincide  exactly  with  the  lower  (apparently  upper)  border 
of  the  cornea,  while  the  examined  eye  is  directed  toward  the  small 
object  in  the  center  of  the  objective  end  of  the  telescope.  Then, 
while  the  head  is  held  in  perfect  immobility,  the  observed  is  directed 
to  look  upward  with  all  his  force.  To  the  beginner  the  movement  may 
not  be  at  first  as  free  as  possible,  but  several  repetitions  will  generally 
result  in  an  effort  which  is  approximately  the  limit. 

As  the  eye  moves  up  (apparently  down)  the  observer  reads  on' 
the  scale  the  extent  through  which  the  border  of  the  cornea  passes. 
(See  Fig.  91.) 

In  examining  the  downward  rotation  it  is  usually  necessary  to 
hold  the  upper  lid  slightly  up  by  the  end  of  the  thumb,  taking  care 
to  bring  no  pressure  on  the  eye  and  to  cause  no  resistance  to  its  free 
movements. 

In  the  lateral  rotations  it  is  essential  to  know  that  the  median 
line  of  the  head  is  at  right  angles  to  the  direction  of  the  telescope. 


1  Fick  speaks  of  the  rotation  of  the  eyes  in  the  horizontal  plane  as  longi- 
tudinal and  those  in  the  vertical  plane  as  latitudinal  directions.  Applying 
this  we  might  express  the  rotation  toward  the  median  plane  as  longitude  — 
a"0,  and  for  a  rotation  toward  the  temple,  +  ,r°.  Also  for  a  rotation  above 
the  plane  of  the  horizon  as  latitude  +  x° ,  and  for  a  rotation  below  that  plane 
as  latitude  —  x°.  In  a  typical  case  of  rotations  the  record  would  read  about 
as  follows:  Long.,  —  45°;  +  40°.  Lat.,  +  35°;  —  40°.  The  more  readily- 
comprehended  terms,  up,  down,  in,  out,  are,  however,  to  be  preferred,  the  posi- 
tion of  departure  being  understood. 


THE  TROPOMETER.  229 

To  this  end  the  teeth  are  fixed  as  nearly  as  possible  midway  between 
the  upright  branches  of  the  stirrup,  then  the  large  adjustable  hoop  is 
attached  to  the  head-rest  and  the  button  is  made  to  press  against  the 
scalp  exactly  over  the  apex  of  the  occipital  protuberance.  (When 
this  is  absent  the  examiner  must  locate  the  central  point  to  the  best 
of  his  judgment.)  Care  is  to  be  observed  that  this  adjustment  is  not 
changed  during  the  examination  of  lateral  rotations.  When  the  ver- 
tical rotations  of  the  two  eyes  are  unequal,  there  is  often  a  corre- 
sponding inequality  in  the  lateral  rotations.  This  latter  inequality 
is  not  necessarily  due  to  any  disproportion  in  the  laterally  acting 
muscles,  since  from  the  very  mechanism  of  the  muscles,  if  there  is  a 
disproportion  in  the  tensions  of  the  vertically  acting  muscles  of  the 
two  eyes,  the  inward  and  outward  rotations  will  be  affected.  This 
is  not  a  hypothetical  statement  only,  it  is  easy  to  observe  the  effects 
of  such  unequal  tensions  of  the  vertically  acting  muscles.  For  ex- 
ample, a  pronounced  diverging  strabismus  may  be  quickly  converted 
into  as  conspicuous  a  converging  strabismus  by  an  advancement 
of  a  superior  or  an  inferior  rectus,  and  this  with  q>  restriction  of  a 
lateral  movement  which  was  before  excessive. 

Also,  if  the  upward  rotations,  though  equal,  are  quite  excessive, 
with  a  corresponding  restriction  of  the  opposite  movement,  or  if  the 
downward  rotations  are  too  great  while  the  upward  are  too  small, 
in  the  act  of  directing  the  eyes  in  the  horizontal  plane  there  may  be 
a  strong  tendency  of  the  visual  lines  to  deviate  laterally,  and  thus,  for 
example,  the  inward  rotations  may  be  much  in  excess  of  those  toward 
the  temples;  and  again,  this  does  not  depend  on  a  normally  faulty 
condition  of  the  converging  muscles,  but  upon  the  tendency  of  the 
eyes  to  turn  to  the  nasal  side  independently  of  any  disproportionate 
influence  of  the  converging  muscles,  and  upon  a  restriction  of  the 
outward  movement  solely  due  to  the  tension  of  the  vertically  acting 
muscles. 

Even  to  this  rule  there  are  occasional  exceptions,  for,  as  it  is 
known  that  the  insertion  of  the  tendons  of  the  eye  muscles  into  the 
surface  of  the  eyeball  is  not  always  uniform;  that  the  insertion  of 
the  vertically  acting  muscles,  for  example,  is  in  exceptional  cases 
placed  more  nearly  to  correspond  with  the  central  sagittal  meridian  of 
the  eye  than  usual,  and  that  in  extremely  exceptional  cases  the  greater 
part  of  the  insertion  line  of  these  same  tendons  may  be  on  the  out- 
side of  that  meridian,  it  will  be  seen  that  the  mechanical  rules  which 


230  ANOMALIES  OF  MOTOR  MUSCLES. 

would  govern  in  the  ordinary  insertions  must  fail  in  these  rare  ex- 
ceptional instances. 

While,  as  it  has  been  shown,  the  rotations  in  various  directions 
differ  in  different  individuals,  the  following  may  be  stated  as  those 
found  under  most  favorable  conditions  of  the  adjustments: — 

Upward— 33°  to  37°. 

Downward — 15°  to  50°. 

Inward — about  50°. 

Outward — about,  or  rather  less  than,  50°   (generally  45°). 

Notwithstanding  the  greater  excursions  of  the  eyes  in  the  hori- 
zontal than  in  the  vertical  directions,  the  variations  from  a  given 
standard  of  rotations  are  greatest  in  the  vertical  direction. 

Even  in  converging  or  diverging  strabismus,  the  departure  from 
the  standard  of  rotations  in  and  out  are  generally,  almost  invariably, 
less  than  the  departure  in  the  same  cases  from  the  standard  of  up- 
ward and  downward  rotations.  Thus,  it  may  happen  that  in  a  case 
of  conspicuous  convergng  squint  the  lateral  rotations  may  be  changed 
from  50°  in  and  45°  out  to  60°  in  and  40°  out.  Only  in  extreme 
cases  is  there,  as  a  rule,  a  greater  change  than  this,  and  the  change 
in  the  orbital  tissues  about  the  inner  canthus,  from  the  habitual 
pressure  of  the  eyeball  at  this  point,  would  fully  account  for  this. 
Yet,  in  the  same  case  the  upward  rotation  may  exceed  the  standard 
of  33°  by  15°  or  more.  And  what  is  of  great  practical  importance 
in  this  connection  is  that,  if  the  tension  of  the  elevator  muscles  is  so. 
far  relaxed  as  to  reduce  the  combined  tension  of  the  elevator  and 
depressor  muscles  to  a  degree  approximating  the  proper  standard, 
the  inward  rotations  of  the  eyes  become  notably  less  and  the  outer 
excursion  is  equally  increased.  It  thus  appears  that  even  in  marked 
converging  squint  there  may  be  no  important  disproportion  between 
the  rotating  ability  of  the  laterally  acting  muscles,  and  that  the 
variation  of  the  excursions  from  the  standard  may  arise  largely,  if 
not  wholly,  from  the  influence  of  the  vertically  acting  forces  and  the 
modifications  of  the  cushion  of  the  eye  from  habitual  pressure. 


TREATMENT   OF  ANOPHORIA  AND   KATOPHORIA.  231 


TREATMENT  OF  ANOPHORIA  AND  KATOPHORIA. 

The  treatment  of  tendencies  and  of  deviations  of  this  class  must 
of  course  depend  on  the  importance  of  their  effects  and  on  the  nature 
of  the  associated  anomalous  conditions  when  they  exist. 

Experience  has  shown  that  a  certain  degree  of  anophoria  may 
be  quite  consistent  with  freedom  from  practical  disturbances  in  the 
form  of  asthenopia  or  other  nervous  reactions  if  there  is  no  compli- 
cation of  an  important  degree  of  declination.  Thus,  one  may  have 
an  upward  rotation  of  38°,  or  even  40°,  without  marked  symptoms. 
But  if  with  this  there  should  exist  declination  of  3°  or  4°  in  one  eye, 
or  divided  between  the  two  eyes,  the  probability  of  nervous  reactions 
would  be  greatly  increased. 

With  katophoria  the  case  is  somewhat  different,  for,  owing  to 
the  tension  on  the  muscles  at  the  back  of  the  head  and  neck,  there  is, 
with  a  moderate  depression  of  the  normal  visual  plane,  a  strong  provo- 
cation to  pain  in  that  region  and  to  other  nervous  symptoms. 

In  my  earlier  experience  with  this  class  of  defects  I  operated 
many  times  by  simple  tenotomy  of  the  superior  or  inferor  recti,  as 
the  case  might  be.  Very  important  relief  followed  the  greater  pro- 
portion of  these  operations,  but  I  soon  discovered  that  these  direct 
operations  did  not  always  accomplish  all  that  could  be  desired,  and 
that  even  unfavorable  results  sometimes  followed.  When  the  influ- 
ence of  declinations  was  recognized,  a  very  marked  advance  in  the 
character  of  the  results  was  observed.  It  is  now  my  custom,  in  case 
of  anophoria,  to  do  the  operation  which  will  be  described  as  extendo- 
contraction1  when  declination  exists — and  I  rarely  operate  for  this 
condition  when  it  does  not — permitting  at  the  same  time  the  muscle 
insertion  on  the  whole  to  fall  back  slightly. 

In  cases  of  katophoria  it  is  much  the  wisest  plan  to  avoid  any 
interference  with  the  inferior  recti  muscles,  since  a  very  slight  irreg- 
ularity in  the  insertion  of  those  muscles  may  induce  a  meridianal 
leaning  in  such  adjustments  as  are  made  in  reading  and  other  close 
work.  It  is  much  better,  if  the  plane  of  regard  is  to  be  raised  by 
operation,  to  do  tendon  contractions,  having  in  view  the  state  of  the 
vertical  meridians. 


1  Section  XLVII,  page  341. 


232 


ANOMALIES  OF  MOTOR  MUSCLES. 


As  a  tentative  means  of  relief,  prisms,  with  the  bases  down  for 
both  eyes,  serve  in  cases  of  anophoria,  and,  with  their  bases  up,  are 
useful  in  katophoria,  but  strong  prisms  cannot  in  such  cases  prove 
anything  but  a  disadvantage,  since  in  the  act  of  convergence  with 
depression  of  the  plane  of  regard,  as  in  reading,  strong  prisms,  of 
necessity,  induce  a  leaning  of  the  images,  and  hence  dispose  to  one  of 
the  most  unpleasant  sources  of  asthenopia. 

The  two  adjoining  figures  will  illustrate  the  habitual  pose  in 
a  case  of  katophoria  and  after  a  change  in  the  mobility  of  the  eyes 
induced  by  operative  means. 


Fig.  92. 


Fig.  93. 


The  figure  (92)  is  not  in  any  way  an  exaggeration;  in  fact, 
the  patient  had  at  neither  sitting  any  intimation  of  the  purpose  of 
the  photographs,  and  in  each  case  assumed  the  pose  which  was  habitual 
with  her  at  the  times  of  the  sittings,  which  were  about  three  weeks 
apart.  The  second  figure  (93)  represents  as  fairly  the  pose  after  a 
relaxation  of  7°  of  each  inferior  rectus. 

It  will  not  be  out  of  place  to  add  that  the  patient,  who  was  an 
epileptic  with  extremely  frequent  and  severe  attacks,  was  free  from 
her  malady  for  more  than  a  year  after  the  operations.  Of  her  later 
condition  I  have  no  knowledge. 


DECLINATIONS.  233 

SECTION  XXVIII. 

Class  II. — Declinations  or  the  Normal  Declinations  of  the 
Retinal  Meridians.1 

DECLINATIONS. 

With  the  advance  in  practical  knowledge  of  the  subject  of  de- 
clination which  arises  from  continued  observation  and  experience, 
the  importance  of  the  subject  is  seen  to  be  increased  in  proportion  as 
acquaintance  with  it  becomes  more  accurate  and  more  extensive.  It 
is  not  necessary  to  compare  the  science  of  declination  with  hetero- 
phoria,  but  it  is  important  to  know  that  the  subjects  are  so  intimately 
associated  and  that  they  are  so  mutually  interdependent  that  the 
study  of  one  cannot  be  successfully  pursued  except  by  the  help  of  the 
other. 

In  my  earlier  contributions  to  the  subject  I  have  emphasized 
many  of  the  disturbances,  both  visual  and  general,  which  may  arise 
from  anomalous  declinations.  A  larger  experience  and  more  ade- 
quately devised  measures  for  the  correction  of  such  anomalies  have 
served  to  confirm  the  view  that  these  conditions  are  of  vital  impor- 
tance, not  only  in  local  ophthalmology,  but  in  the  realm  of  general 
affections  of  the  body. 

Experience  has  also  shown  that  a  practical  exercise  of  a  knowl- 
edge of  this  subject  has  a  wider  field  of  application  than  could  have 
been  shown  at  an  earlier  stage  of  the  investigation. 

In  the  case  of  certain  persons  when  diplopia  is  induced  by  a 
prism,  certain  phenomena  other  than  the  simple  displacement  of  one 
image  by  the  prism  are  revealed.  One  of  these  is  a  leaning  of  one  of 
the  images,  or  of  both,  independent  of  and  generally  much  out  of 
proportion  to  any  leaning  which  would  be  induced  by  the  direct  action 
of  the  prism.  This  phenomenon,  although  rarely  observed,  will  serve 
to  introduce  us  to  an  interesting  and  important  subject. 

Suppose  that  the  diplopia  is  induced  by  placing  a  prism  with 
its  base  in  before  the  right  eye.  If,  now,  the  object  used  in  the  ex- 
periment is  a  lighted  candle  situated  at  twenty  feet  from  the  eyes  and 
erect,  while  the  head  of  the  observer  is  in  the  primary  position,  in- 


1  For  earliest  papers  on  this  subject,  see  Archives  of  Ophthalmology,  vol. 
xxvi,  No.  2,  1897,  and  vol.  xxviii.  No.  1.  1899;  Ophthalmic  Record,  May,  1898; 
New  York  Medical  Journal,  February  16  and  23,  1901. 


234  ANOMALIES  OF  MOTOR  MUSCLES. 

dependent  of  whether  the  two  images  of  the  candle  are  seen  in  the 
same  horizontal  plane,  one  or  both  images  may  appear  to  lean  toward 
or  away  from  each  other  at  the  top.  Such  leanings  are,  as  a  rule, 
only  observed  when  the  meridians  of  the  retina  or  retinas  of  the 
observer  deviate  to  a  very  pronounced  degree,  and  when  the  observer 
has  much  difficulty  in  bringing  the  images  to  an  upright  position. 
Slight  conditions  of  this  sort  are  rarely  discovered  in  this  way. 

It  was  by  experiments  somewhat  of  this  nature,  but  made  with 
upright  adjustable  lines,  that  Volkmann,  Helmholtz,  Hering,  Bon- 
ders, LeConte,  and  others,  each  by  experiments  different  in  detail  but 
similar  in  principle  to  the  others,  arrived  at  the  conclusion  that  for 
all  eyes  the  vertical  meridians  normally  leaned  out.  Thus,  Bonders 
says1 : — 

"Hering  ('Beitrage  zur  Physiologic/  p.  175)  has  stated  that  in 
the  primary  position  his  vertical  meridians  diverge  above;  and  later 
he  has  declared  that  this  is  true  for  all  eyes." 

That  this  view,  which  was,  when  Bonders  wrote,  accepted  by  all, 
is  incorrect  has  been  shown  elsewhere.  Yet,  beyond  question  such  a 
condition  did  exist  in  the  cases  of  these  observers.  Leanings  had 
been  therefore  recognized,  but  their  nature  was  not  understood  until 
it  was  shown  by  myself 2  in  1897.  The  condition  believed  by  these 
observers  to  be  a  physiological  characteristic  was  shown  to  be  in  their 
cases  personal  peculiarities. 

The  purpose  here  is  to  examine  the  phenomenon.  Let  us  assume 
that  in  our  experiment  the  image  of  the  right  eye,  that  before  which 
the  prism  is  placed,  is  erect,  while  the  image  of  the  left  eye  leans 
with  the  top  toward  the  right  (in).  We  conclude  that,  as  a  matter 
of  fact,  the  vertical  meridian  of  that  eye  leans  out  above.  For  the 
apparent  leaning  will  be  exactly  opposite  the  real  leaning.  This  is 
readily  explained  on  principles  of  physiological  optics  and  may  be 
easily  demonstrated  by  tilting  the  candle  toward  the  left  when  the 
left  eye  image  will  appear  erect.  In  our  experiment  we  are  ignoring 
both  the  movement  and  deflection  of  the  image  which  might  arise 
from  the  use  of  a  prism.  Of  course,  such  a  deflection  might  induce 
the  phenomenon  of  which  we  speak. 

This  phenomenon,  as  just  remarked,  is  not,  as  was  formerly 
supposed,  the  result  of  a  condition  common  to  all  eyes.  It  is  the 


'Archiv  fiir  Ophth.,  xxi,  3,  103. 

2  Archives  of  Ophthalmology,  vol.  xxvi,  November  2,  1897. 


DECLINATIONS. 


235 


result  of  an  anomalous  condition  in  the  same  way  that  hypermetropia 
is  anomalous,  and  the  anomaly  is  not,  as  was  supposed,  confined  to 
one  direction;  it  may  be  a  leaning  out  of  the  meridians  of  each  eye 
or  in  of  each  eye,  or  a  leaning  in  of  one  eye  and  out  of  the  other, 
or  the  vertical  meridian  of  one  eye  may  be  exactly  erect  while  that 
of  the  other  leans. 

Leaving  the  rude  and  imperfect  illustration  drawn  from  the 
double  images  of  the  candle,  we  are  prepared  to  define  the  terms  at 
the  head  of  this  section  and  to  examine  into  the  nature  of  the  phe- 
nomena which  they  designate. 


DEFINITION. 

By  Declination,  or  Normal  Declination  of  the  Retinal  Meridians, 
is  meant  the  deviation  of  the  vertical,  horizontal,  or  any  given  meri- 
dian of  the  eye  from  the  corresponding  meridian  of  external  space 
when  the  line  of  regard  is  directed  parallel  to  the  median  plane  and 
in  the  plane  of  the  horizon,  the  head  being  exactly  erect  or,  more 
technically,  in  the  primary  position. 

To  make  the  definition  clear  we  may  refer  to  the  diagram. 
(Fig.  94.) 

Suppose  the  circle  eac,  fbd  to  represent  the  equator  of  the  eye- 
ball, and  the  line  ab  to  represent  the  normal  position  of  the  vertical 
meridian  of  the  eye,  the  line  of  regard  being  directed  as  stated.  If 
this  line  corresponds  with  the  vertical  meridian  of  surrounding  space 
there  is  no  declination  of  it,  and  consequently  none  of  any  meridian.1 


1  But  Helmholtz  believed  that  the  horizontal  meridian  might  be  coincident 


236  ANOMALIES  OF  MOTOR  MUSCLES. 

But  should  the  eye  be  rolled  upon  its  antero-posterior  axis  so 
that  this  vertical  meridian  would  correspond  with  the  position  cd 
or  ef,  it  is  evident  that  in  either  case  the  vertical  meridian  and  all 
other  meridians  of  the  eye  would  no  longer  correspond  in  position 
with  meridians  of  the  same  name  in  surrounding  space.  In  either 
case  there  would  result  what  I  have  called  a  declination.  If  in  such 
a  case  the  top  of  the  meridian  line  cd  leans  toward  the  temple,  it  is 
termed  a  positive  (  +  )  declination,  while  if  the  line  ef  leans  toward 
the  nose,  it  represents  a  negative  ( — )  declination. 

There  are  normal  declinations  and  declinations  from  disease  or 
injury.  It  is  therefore  necessary  to  know  what  a  normal  declination 
is  not.  It  is  not  the  tilting  of  the  meridians  which  results  from  any 
paralysis,  paresis,  or  insufficiency  of  any  eye  muscle  or  set  of  mus- 
cles. In  other  words,  it  is  not  a  disease.  It  is  a  normal,  though 
unfavorable,  condition.  It  should  be  called  an  anomalous  in  contra- 
distinction to  a  pathological  declination.  Hypermetropia  was,  before 
the  era  of  Bonders,  regarded  as  a  "weakness"  of  the  eyes;  now  it 
is  known  that  the  condition  has  no  dependent  relation  to  weakness  or 
strength  of  any  part  of  the  eyes.  No  more  are  the  declinations  which 
we  are  to  consider  dependent  upon  the  strength  or  weakness  of  any 
structure.  They  are  anomalies  in  the  sense  that  they  are  deviations 
from  a  rule  which  should  prevail  where  the  typical  conditions  are 
present.  They  are  anatomical  peculiarities  which  vary  from  the  ideal 
state,  but  are  probably  much  more  commonly  found  than  is  the 
typical  state.  Since  anomalous  declinations  are  frequent,  although 
not  generally  to  be  detected  by  such  an  experiment  as  we  have  men- 
tioned, and  since  pathological  declinations  are  rare,  the  term  "declina- 
tion," when  used  alone,  should  apply  to  the  first  class  only,  while  to 
designate  the  tiltings  from  disease  or  injury  the  limiting  term  "patho- 
logical" should  be  added.  Nor  should  the  term  "declination"  be  con- 
founded with  the  term  torsion,  which  has  long  been  applied  to  the 
rotations  of  the  meridians  when  the  eye  passes  from  the  primary  and 
horizontal  position  to  some  position  in  which  the  line  of  regard  is 
directed  to  some  point  not  in  the  primary  position  or  horizontal  plane. 
Nor  does  the  term  declination  apply  to  the  conditions  reported  to 
have  been  found  by  means  of  prisms  when  the  eyes  were  in  con- 
vergence and  the  plane  of  regard  in  some  undefined  plane.  Nat- 


with  the  horizon,  while  the  vertical  meridian  was  only  an  "apparent"  one,  and 
deviated. 


DECLINATIONS.  237 

urally,  such  conditions  when  not  directly  induced  by  the  prisms 
might  belong  to  the  class  of  torsions  or  to  some  other  undetermined 
condition. 


INSTRUMENTS  FOR  DETERMINING  DECLINATIONS. 

The  crude,  indefinite,  and  inaccurate  methods  which  were  in 
vogue  for  determining  the  approximate  directions  of  the  tiltings  of 
images  in  cases  of  paralysis  or  injury  of  the  eye  muscles  previous  to 
the  introduction  of  the  clinoscope  find  no  place  in  the  examinations 
necessary  to  a  correct  determination  and  valuation  of  normal  declina- 
tions. 

The  visual  act  must  be  confined  to  the  test  line  alone,  and  all 
view  of  objects  outside  the  tubes  of  the  instrument  must  be  excluded, 
in  order  that  the  eyes  may  be  free  from  the  instinctive,  or  automatic, 
effort  to  adjust  themselves  with  reference  to  the  position  of  external 
objects.  The  lines  of  sight  of  the  two  eyes  must  be  absolutely  in  the 
same  horizontal  plane,  and  these  sight  lines  are  to  be  neither  in  con- 
vergence nor  divergence,  except  to  meet  certain  special  contingencies. 

These  and  other  important  conditions  are  met  in  the  use  of  the 
clinoscope. 

The  clinoscope -(Fig.  95)  is  composed  essentially  of  two  hollow 
tubes,  each  of  which  has  at  one  end  a  minute  pinhole  opening  through 
which  the  eye  can  look,  and  at  the  other  end  a  translucent  disc  on 
which  is  drawn  a  line,  in  the  case  of  one  tube  from  the  center  straight 
up,  and  in  that  of  the  other  tube  straight  down. 

These  tubes  are  so  adjusted  on  a  standard  that  they  can  be  placed 
and  maintained  in  the  same  horizontal  plane,  which  is  indicated  by 
a  spirit  level,  but  from  end  to  end  they  can  be  directed  horizontally 
or  up  or  down.  They  can,  as  above  intimated,  be  made  to  converge  or 
diverge  to  meet  certain  contingencies. 

The  tubes  rotate  on  their  long  axes,  and  a  pointer  attached  to 
each  tube  indicates  on  a  scale  the  extent  to  which  the  tube  is  rotated. 
The  small  sight  openings  are  so  adjustable  that  the  distance  between 
them  may  be  suited  to  the  interpupillary  distance  of  different  per- 
sons. For  the  accommodation  of  those  who,  on  account  of  pres- 
byopia, myopia,  or  any  high  degree  of  refractive  error,  cannot  see  at 
the  distance  of  the  test  objects  from  the  eyes,  there  are  clips  in  which 
refracting  glasses  may  be  placed.  The  sight  openings  being  very 
small  and  exactly  in  the  same  horizontal  plane,  there  can  be  no  doubt 


238  ANOMALIES  OF  MOTOR  MUSCLES. 

as  to  the  erect  position  of  the  median  plane  of  the  head  when  the  two 
eyes  are  seeing,  each  through  its  appropriate  sight  opening,  any  exist- 
ing hyperphoria  being  corrected. 


Fig.  95. — The  Clinoscope. 

Any  device  for  testing  declination  which  does  not  provide  for 
the  exclusion  of  surrounding  objects  from  the  field  of  view  and  which 
does  not  also  secure  an  absolutely  erect  position  of  the  head  is  worse 
than  worthless,  since  it  must  be  misleading. 

To  meet  the  exigencies  of  cases  of  greater  or  less  degrees  of 
amblyopia,  as  in  squint  or  extreme  myopia,  it  was  found  necessary 
to  devise  what  I  have  called  the  "lens  clinoscope,"  an  indispensable 


DECLINATIONS. 


239 


instrument,  but  one  which  cannot  take  the  place,  in  ordinary  cases, 
of  the  clinoscope. 

Method  of  Using  tlie  Clinoscope. — The  instrument  is  to  be  so 
adjusted  in  respect  to  height  that  the  sight-holes  will  be  on  a  level 


Fig.  96. — Objective  Lines  for  the  Clinoscope.1 

with  the  eyes  of  the  examined  person  when  sitting  erect.  This  is  best 
accomplished  by  the  use  of  an  adjustable  table.  The  tubes  may  be 
exactly  parallel  or  they  may,  in  certain  cases,  be  made  to  converge 


Fig.  97. — The  Lens  Clinoscope. 

very  slightly,  thus  making  the  distant  point  at  8  or  10  feet  instead  of 
infinite  distance.  Under  other  exceptional  circumstances  they  may 
be  made  to  diverge.  The  tubes  must  be  brought  to  an  exact  level 
with  each  other  as  shown  by  the  spirit  level. 

Unless  the  subject  of  the  examination  is  unqble  to  see  the  test 


1  For  purposes  of  physiological  research  objective  diagrams  of  many 
designs  may  be  connected  with  the  clinoscope,  but  for  practical  purposes  the 
above  is  sufficient,  and  it  is  important  not  to  disarrange  the  working  ob- 
jectives. 


240  ANOMALIES  OF  MOTOR  MUSCLES. 

lines  of  the  tubes,  on  account  of  presbyopia  or  high  refractive  error, 
no  glasses  should  be  used,  and  when  glasses  are  necessary  the  weakest 
that  will  enable  the  person  to  see  the  lines  clearly  should  be  placed 
in  the  clips.  A  prism  for  the  correction  of  hyperphoria  may  also  be 
required.  The  glasses  should  not  be  worn,  since,  if  a  strong  glass 
should  not  be  held  exactly  at  a  right  angle  with  the  axis  of  the  tube, 
the  lens  would  itself  induce  a  deflection  of  the  image. 

The  examiner  must  be  sure  that  the  examined  person  sees 
through  both  openings  simultaneously  and  that  the  view  of  both 
images  is  maintained  throughout  the  examination,  otherwise  there 
can  be  no  certainty  that  the  head  is  precisely  erect. 

When  the  examined  person  has  secured  a  good  view  of  both  the 
test  lines  he  should  endeavor,  if  they  do  not  at  once  unite,  to  induce 
them  to  do  so  as  in  a  stereoscope.  Some  people  do  not  succeed  in 


To  Test  the  Clinoscope. — Before  using  the  clinoscope  the  test  lines  should 
be  adjusted  with  great  care,  and  it  should  be  postively  known  that  when  the 
pointers  are  at  the  zero  mark  on  the  scale  the  lines  on  the  objectives  are 
absolutely  vertical. 

To  adjust  the  objectives  the  following  method  may  be  adopted: — 
Place  the  clinoscope  on  a  narrow  table  which  will  allow  the  examiner  to 
look  through  the  eyepiece  at  one  end  and  permit  a  plumb  line  to  swing  free 
at  the  objective  end.     Let  a  very  fine  thread,  to  which  is  attached  a  weight 


Method  of  Testing  the  Clinoscope.    P,  The  plumb  line. 

sufficient  to  render  it  tense,  fall  in  front  of  the  objective  and  almost  in  contact 
with  it.  The  thread  should  be  at  least  two  feet  in  length.  Open  the  shutter 
at  the  eyepiece  so  as  to  give  a  free  view,  bring  the  instrument  to  an  exact 
level  as  shown  by  the  spirit  level,  set  the  pointers  exactly  at  zero,  then,  the 
screws  of  the  objectives  being  somewhat  loosened,  adjust  the  line  exactly 
parallel  with  the  image  of  the  plumb  line  thread.  Do  not  let  the  line  and 
thread  image  come  in  contact.  Leave  a  slight  space  so  as  to  observe  exact 
parallelism.  When  the  line  is  exactly  upright  make  the  screws  tight  ani 
examine  again  to  see  that  the  objective  has  not  been  disarranged. 


DECLINATIONS.  241 

this,  in  which  cases  the  examination  may  go  on  with  the  images  sepa- 
rated, but  it  is  less  satisfactory. 

When  the  apparent  vertical  position  of  the  lines  has  been  at- 
tained, the  examiner  should  move  them  more  or  less  backward  and 
forward,  in  order  that  the  true  position  may  be  more  positively  located. 
Few  people  can  arrive  at  a  satisfactory  conclusion  regarding  the 
position  of  the  lines  at  the  first  trial,  but  after  a  day  or  two  the  tests 
become,  for  nearly  all  intelligent  people,  remarkably  uniform. 

In  a  former  section  (Section  XXVI)  it  has  been  shown  that 
the  plane  of  least  leaning  of  the  meridians  depends  upon  the  presence 
or  absence  of  anophoria  or  katophoria.  For  very  precise  investigations 
the  clinoscope  should  be  adjusted  with  reference  to  the  normal  plane 
of  vision.  In  practice,  when  the  extent  of  deviation  of  the  plane  of 
vision  from  the  horizon  is  not  great,  a  slight  adjustment  of  the  head 
while  the  tubes  remain  horizontal  will  serve  to  avoid  material  torsions. 

Results  of  Examinations. — Previous  to  the  investigations  by  the 
clinoscope  a  belief  had  prevailed  among  physiologists  that  there  was, 
in  healthy  eyes,  a  fixed  and  definite  position  for  the  meridians  o"f  the 
eye,  a  physiological  characteristic  of  the  construction  of  the  retina, 
and  that  this  position  was  general,  if  not  universal.  Helmholtz,  Bon- 
ders, Yolkmann,  Meissner,  and  others  had  devised  means  for  the 
investigation  of  the  facts,  all  of  which  means  were  imperfect  and 
most  of  which  were  misleading,  and  most  of  these  investigators  agreed 
that  normally  there  existed,  for  the  vertical  meridian,  a  leaning  out 
of  about  1  i/40,  while  the  horizontal  meridian  was  supposed  to  coin- 
cide exactly  with  the  real  horizon.  These  leanings  were  not  supposed 
to  be  personal  peculiarities,  but  essential  elements  in  the  physiology 
of  the  retina. 

One  of  the  first  results  of  the  investigations  by  the  clinoscope 
was  the  demonstration  that  the  positions  of  the  vertical  and  hori- 
zontal meridians  leaned,  when  either  leaned,  in  corresponding  direc- 
tions and  to  an  equal  extent.  What  was  of  far  greater  importance, 
it  was  found  that  the  leanings  of  the  meridians  were  as  varied  and 
as  characteristic  of  the  individual  as  the  refraction  of  the  eyes. 

The  clinoscope  shows  that  in  some  persons  the  vertical  meridian 
of  one  eye  corresponds  with  an  exact  vertical  line,  while  that  of  the 
other  eye  leans  from  one  degree  to  many  degrees.  In  other  cases  the 
vertical  meridian  of  each  eye  leans  in  the  same  direction,  that  is,  each 
to  the  right  or  each  to  the  left,  and  this  leaning  is  nearly  equal  in 
the  two  eyes.  In  still  other  cases  the  meridians  lean  in  opposite 


242  ANOMALIES  OF  MOTOR  MUSCLES. 

directions,  that  of  one  eye  to  the  right,  that  of  the  other  eye  to  the 
left.  In  extent  there  is  great  variation,  some  cases  showing  the 
meridian  of  each  eye  very  nearly  erect,  while  others  will  show  the 
meridians  in  both  eyes  leaning  as  much  as  six  or  even  ten  degrees. 

It  is  these  leanings  which  I  have  called  declinations.  They  are 
not,  as  has  already  been  said,  torsions,  which  term  has  a  well-estab- 
lished meaning,  the  phenomena  to  which  it  refers  being  widely  dif- 
ferent from  those  under  discussion.  Torsion  results  from  an  active 
adjustment  of  the  eye  and  corresponds  to  the  position  to  which  the 
eye  is  moved.  Declinations,  on  the  other  hand,  are  purely  passive 
states  to  be  determined  when  the  lines  of  regard  are  fixed  in  the  pri- 
mary position. 

In  normally  healthy  eyes  the  leaning  of  a  meridian  may  vary 
according  to  the  automatic  tension  which  may  be  exerted.  Hence  it 
is  found  that  very  high  degrees  of  declination  are  more  frequently 
manifest  in  persons  who  have  passed  fifty  years  of  age  than  in  those 
who  are  younger.  Hence  also  there  is  sometimes  a  variation  which 
appears  to  depend  on  the  physical  condition  of  an  individual  at  dif- 
ferent times. 

I  have  compared  these  anomalies  of  declination  to  those  of  re- 
fraction. As  there  are  few  eyes  without  some  error  of  refraction, 
so  there  are  few  in  which  the  insertions  of  the  muscles  are  so  ideal 
that  there  is  no  declination;  and,  as  slight  refractive  errors  may  be 
disregarded,  so  slight  declinations  may  have  little  practical  signifi- 
cance. Even  high  degrees  of  declination  seem  in  certain  instances, 
like  certain  cases  of  high-grade  hypermetropia,  to  exert  no  appreciable 
injurious  influence.  Yet,  as  a  rule,  as  in  refraction,  the  higher  the 
grade  of  the  anomaly  the  greater  the  resulting  nervous  disturbance. 

SOME  or  THE  RELATIONS  BETWEEN  DECLINATIONS  AND 
HETEROPHORIA. 

Long  before  the  principles  of  declination  were  recognized  I  be- 
came impressed  with  the  belief  that  many  of  the  phenomena  of 
heterophoria  and  heterotropia  were  secondary  to  some  other  condition 
than  the  condition  which  was  most  manifest.  Thus,  for  several  years 
I  had  often  expressed  in  my  writings  the  thought  that  there  were 
few,  if  any,  cases  of  original  exophoria,  and  I  diligently  endeavored 
to  learn  the  true  nature  of  the  anomaly.  Certain  cases,  too,  of  hyper- 
phoria  seemed  to  me  not  to  be  essentially  such,  and  many  cases  of 


DECLINATIONS  AND  HETEROPHORIA.  243 

esophoria  were  so  contradictory  in  their  phenomena  that  there  seemed 
to  be  demanded  a  further  element  to  account  for  them. 

The  clinoscope  has  thrown  a  remarkable  light  upon  these  ques- 
tions. A  few  of  them  are  answered  with  ease,  since  the  relations 
between  the  revelations  by  the  clinoscope  and  those  of  the  phorometer 
appear  to  be  quite  simple.  In  other  cases  these  relations  are  much 
more  complicated,  yet,  in  general,  quite  susceptive  of  explanation. 

The  relationship  -between  declination  and  exophoria  is  perhaps 
the  most  easy  to  comprehend,  and  a  study  of  these  relations  is  most 
interesting.  In  exophoria  there  is,  as  a  rule,  positive  (-)-)  declina- 
tion of  both  eyes,  and  the  extent  is  nearly  equal  in  each.  The  excep- 
tions to  this  rule  are  rare,  and  even  these  apparent  exceptions  are,  after 
close  investigation,  usually  found  not  to  be  exceptions  at  all.  Still 
the  fact  is  to  be  recognized  that  in  some  instances  there  may  be  a 
high  degree  of  -{-  declination  for  one  eye  with  little  or  none  or  even 
slight  —  declination  for  the  other.  Conversely  to  the  general  propo- 
sition, positive  (-(-)  declinations  of  both  eyes  is  strongly  suggestive 
of  exophoria. 

In  the  rotation  of  the  eyes  upon  their  long  axes,  in  the  effort  to 
effect  parallelism  of  the  vertical  meridians,  each  eye  is  forced  down- 
ward and  outward.  The  downward  movements,  if  they  are  equal, 
have  little  influence  in  inducing  heterophoria,  but  when  the  declina- 
tion to  be  corrected  is  considerable,  the  effect  upon  the  outward  swing 
of  the  eyes  may  be  very  considerable.  As  each  line  of  regard  is  forced 
outward  the  parallelism  of  the  lines  of  regard  is  sacrificed  to  that 
of  the  vertical  meridians  and  exophoria  results. 

It  will  be  seen  also  that,  if  the  leanings  of  the  meridians  are  each 
positive  but  unequal,  one  eye  would  be  forced  outward  and  downward 
more  than  the  other,  and  hyperphoria  might  result.  These  theoretical 
views  of  the  adjustments  correspond  exactly  with  the  results  of  prac- 
tical experience  when  the  phorometer  and  the  clinoscope  are  used 
together.  The  manifestations  of  heterophoria  are  not  always  present 
when  the  inducing  causes  exist. 

When  operating  for  exophoria  by  slight  tenotomies  before  the 
use  of  the  clinoscope,  I  observed  that,  as  a  rule,  the  tendon  of  the 
externus  was  rarely,  if  ever,  found  tense.  It  was  hard  to  believe  that 
the  exophoria  could  be  the  result  of  the  predominance  of  force  of  this 
muscle,  which  was  so  often  found  much  relaxed.  Later,  when  the 
tropometer  was  brought  to  the  attempted  solution  of  these  questions, 
it  was  found  that  there  was,  in  most  cases,  no  excess  of  rotating*power 


244  ANOMALIES  OF  MOTOR  MUSCLES. 

in  the  extern!  or  any  deficiency  of  rotating  ability  in  the  interni.  It 
was  noticeable  also  that  it  was  no  uncommon  thing  that  what  was 
apparently  a  successful  correction  of  the  exophoria  was  only  a  tem- 
porary one,  and  that  the  defect  was  apt  to  return  in  a  few  weeks  or 
even  after  a  few  days  in  almost  as  high  degree  as  before  the  operation. 
It  was  in  many  cases  deemed  better  to  leave  uncorrected  a  marked 
degree  of  exophoria  than  to  reduce  the  rotating  ability  of  the  externi, 
either  by  tenotomy  or  by  a  contraction  of  the  interni,  to  an  extent 
sufficient  to  permanently  abolish  the  exophoria.  With  the  advent  of 
the  clinoscope  much  light  was  thrown  upon  this  whole  subject.  With 
a  knowledge  of  the  declinations  and  their  effects  we  may  now  look  for 
a  relief  from  exophoria  without  restricting  the  action  of  any  muscle 
and  with  a  reasonable  expectation  of  permanency  of  result. 

The  hyperphoria  which  may  result  when  there  is  somewhat  un- 
equal leaning  of  the  meridians  in  the  two  eyes  has  been  referred  to 
above.  In  many  cases  of  hyperphoria  a  declination  of  several  degrees 
may  be  found  for  one  eye  while  the  other  will  be  either  without  de- 
clination or  with  very  much  less  than  the  first  and  usually  of  the 
same  sign.  An  example  of  this  will  not  be  out  of  place  here. 

In  a  case  of  long-standing  vertical  diplopia  there  was,  during 
four  successive  days'  testings:  Eight  hypertropia  10°  in  the  primary 
position  with  increased  hypertropia  looking  down  30°  or  up  20°.  In 
alternate  exclusion  the  deviation  appeared  even  greater  than  that 
shown  by  the  phorometer.  The  rotation  up,  as  shown  by  the  tropome-r 
ter,  was,  for  the  right  eye  40°  and  for  the  left  36°.  It  Avould  seem 
that  this  was  pre-eminently  a  case  for  a  tenotomy  of  the  superior 
rectus  of  the  right  eye.  Yet,  as  there  was  declination  -f-  6°  of  the 
left  eye  and  only  -)-  1°  of  the  right,  I  determined  to  do  an  operation 
on  the  internus  of  the  left  eye  with  only  the  declination  in  view,  for 
there  was  no  marked  exophoria  or  esophoria.  The  operation  was 
successful  in  correcting  the  declination  to  within  2°,  and  on  the  fol- 
lowing day  I  had  the  satisfaction  of  finding  that  there  was  easy  single 
vision  with  less  than  2°  hyperphoria  and  with  no  esophoria  or  exo- 
phoria. After  many  weeks  had  passed  the  hypertropia  had  not  again 
manifested  itself. 

Such  a  case  is  of  much  interest  in  illustrating  the  dominating 
influence  of  declination  even  in  extreme  hypertropia.  It  is  also  inter- 
esting as  an  illustration  of  the  daily  experience  in  removing  the  con- 
ditions of  heterophoria  and  even  strabismus  by  the  simple  correction 
of  declination.  The  example  a^so  shows  how  even  the  upward  rota- 


DECLINATIONS  AND  HETEROPHORIA.  245 

tion  may  be  influenced  by  the  declination,  for  after  the  operation 
on  the  internus  the  upward  rotation  of  the  two  eyes  was  nearly 
equal.  This  case  is  stated  not  as  an  exceptional  instance,  but  as  an 
illustration  of  daily  experience. 

In  esophoria  declination  is  almost  uniformly  found  in  both  eyes, 
and  the  leanings  of  the  meridians  are  conjugate.  If  the  declination 
is  plus  for  the  right  eye,  it  is  minus  for  the  left,  and  most  frequently 
the  leanings  are  approximately  of  nearly  the  same  extent.  The  greater 
the  extent  of  declination,  usually,  the  greater  the  degree  of  esophoria. 
If,  however,  there  is  positive  declination  of  one  eye  of  a  considerable 
degree  and  of  the  other  of  a  very  slight  degree,  or  only  a  very  slight 
negative  declination,  the  images,  in  examining  by  the  phorometer, 
may  swing  from  a  high  to  a  low  degree  of  esophoria  or  from  esophoria 
to  exophoria,  the  position  of  the  images  depending  in  such  a  case  on 
the  effort  to  make  vertical  the  vertical  meridian  of  one  or  of  the 
other  eye. 

Thus  it  appears  that  the  different  forms  of  heterophoria  are  asso- 
ciated with  different  forms  of  declination,  and  experience  has  shown 
that  in  a  large  proportion  of  cases  a  relief  to  the  declination  is  fol- 
lowed at  once  by  a  relief  to  the  heterophoria.  In  certain  unusual 
cases  it  will  be  found  that  each  eye  will  rise  many  degrees  when  a 
screen  is  placed  before  it.  Even  when  any  excess  of  upward  rotation 
has  been  corrected  the  phenomenon  remains.  Here  the  upward  turn- 
ing is  due  to  the  declination  of  the  opposite  eye  and  it  will  remain 
even  after  the  eyes  are  both  too  low,  unless  the  declination  is  cor- 
rected. 


EMPIRICAL  SCHEME  FOR  SOME  OF  THE  RELATIONS  OF 
DECLINATION  AND  HETEROPHORIA. 

The  following  diagrams  with  the  assumed  action  of  the  muscles  in  cor- 
recting the  declinations  will  suggest  some  of  the  forms  of  heterophoria  which 
may  result  from  declinations.  It  is,  however,  to  be  remembered  that  the 
comparative  action  of  the  various  muscles  may  so  modify  the  results  that 
these  rules  may  not  apply  in  an  individual  case.  The  scheme  is  therefore 
suggestive  rather  than  absolute,  and  it  also  often  happens  that  in  cases  of 
marked  declination  where  no  heterophoric  conditions  are  manifest  a  slight 
change  of  the  equation  may  modify  the  result  to  an  important  extent. 


246 


ANOMALIES  OF  MOTOR  MUSCLES. 


Fig.  98. 

Right  Eye — The  muscles  brought  into  action  are:  — 

The  inferior  oblique,  rotates  the  eye  out  and  up  and  rolls  it  to  the  right. 

The  inferior  rectus,  which  draws  the  eye  downward  and  rolls  it  to  the 
right. 

Result:  Exophoria,  unless  the  internus  is  brought  into  action  to  over- 
come the  outward  rotation,  in  which  case  the  synergic  action  of  the  left 
internus  may  induce  esophoria. 


Fig.  99. 


Right  Eye — Muscles  brought  into  service  are: — 

The  superior  oblique,  which  rotates  the  eye  down  and  out  and  rolls  it  to 
the  left. 

Left  Eye — The  superior  rectus,  which  rotates  the  eye  down  and  out  and 
rolls  it  to  the  right. 

Results:  Except  when  the  inferior  recti  are  brought  into  action  to 
overcome  a  marked  anophoria,  the  result  is  exophoria. 


DECLINATIONS  AND  HETEROPHORIA. 


247 


Fig.  100. 


Right  Eye — Muscles  involved:  — 

Inferior  oblique,  rotates  eye  up  and  out  and  rolls  eye  to  right. 
Inferior  rectus,  rotates  eye  down  and  rolls  it  slightly  to  right. 
Left  Eye — Muscles  involved: — 

Superior  oblique,  rotates  eye  down  and  out  and  rolls  it  to  right. 
Results  often  in  right  hyperphoria,  but  if  the  negative  declination  of  the 
right  is  less  than  the  positive  of  the  left,  the  result  is  esophoria. 


R 


Fig.  101. 


Right  Eye — Muscles  involved:  — 

Superior  oblique,  rotating  eye  down  and  out  and  rolling  it  to  left. 

Superior  rectus,  rotating  eye  up  and  slightly  in  and  rolling  eye  to  left. 

The  internal  rectus  may  act  to  neutralize  the  outward  action  of  the 
oblique,  which  may  be  in  excess  of  what  is  neutralized  by  the  superior  rectus. 

Result:  Esophoria  and,  if  left  superior  rectus  acts  synergically  with 
the  right,  left  hyperphoria. 


248  ANOMALIES  OF  MOTOR  MUSCLES. 


HETEROTROPIA  OR  STRABISMUS  AND  DECLINATION. 

The  principles  which  apply  to  the  relations  between  heterophoria 
and  declinations  apply  also  to  strabismus.  The  conditions  differ  in 
respect  to  the  degree  of  declinations  and  also,  in  general,  in  respect 
to  the  vertical  rotations.  The  causative  conditions  of  heterotropia 
are  usually,  not  only  exaggerations  of  those  of  heterophoria,  but  the 
conditions  are  also  more  complicated. 

After  some  experience  in  the  use  of  the  tropometer  I  found 
that  in  nearly  every  case  of  converging  strabismus  there  was  not 
only  excessive  upward  rotation  of  the  eyes,  but  that  this  rotation  was, 
in  fact,  in  most  cases  extravagant.  For  example,  instead  of  a  rota- 
tion up  of  about  33°,  which  investigation  and  experience  had  shown 
was  the  most  favorable,  in  cases  of  converging  strabismus  it  was  not 
uncommon  to  find  the  upward  rotation  as  much  as  50°  or  even  55°. 
A  reduction  of  this  excessive  upward  rotation,  this  anophoria,  served, 
in  a  number  of  cases  of  marked  squint,  to  relieve  the  defect  without 
interference  with  the  laterally  acting  muscles,  and  there  seemed  to 
have  been  found  a  condition  a  modification  of  which  promised  a 
relief  in  strabismus  without  an  unfavorable  restriction  in  the  action 
of  any  muscle.  A  larger  experience  showed  that,  while  there  was  in 
this  thought  an  important  truth,  there  remained  an  element  of  un- 
certainty with  respect  to  results  which  was  of  great  practical  impor- 
tance. 

.{  f-  With  the  introduction  of  the  clinoscope  new  observations  were 
made,  and  it  was  soon  found  that  in  nearly  all  cases  in  which  there 
was  a  very  excessive  range  of  rotations  in  the  vertical  direction  there 
were  also  unusual  degrees  of  declinations.  Applying  these  new  facts 
to  those  which  had  been  previously  observed,  there  arose  the  reason- 
able hypothesis  that  the  excessive  declinations  combined  their  influ- 
ence with  the  excessive  vertical  rotations  to  induce  the  strabismus. 

Close  observation  and  added  experience  have  confirmed  this 
hypothesis,  which,  in  the  light  of  abundant  practical  facts,  has  now 
become  a  demonstrated  proposition.  It  will  be  seen  as  we  proceed 
that  it  supplies  a  rational  method  for  the  cure  of  converging  or 
diverging  strabismus  without  the  disability  which  has  invariably 
resulted  to  the  tenotomized  (or  contracted)  musc]es  in  the  older 
methods  of  operating  for  squint. 

It  may  be  said  that,  as  a  rule,  to  which  rule,  however,  there  are 


LOCAL  SYMPTOMS   OF  DECLINATIONS.  249 

exceptions  in  respect  to  the  upward  rotations,  there  is  in  convergent 
squint  excessive  upward  rotation  with  extreme  conjugate  declination, 
that  is,  with  positive  declination  for  one  eye  and  negative  for  the  other, 
or,  rarely,  the  declination  for  both  may  be  of  one  sign  but  differing 
greatly  in  degree.  In  some  of  the  cases  of  the  latter  class  there  is 
alternating  squint.  If  the  eye  with  the  extreme  positive  declination 
is  fixed  upon  the  object,  there  will  be  converging  squint,  while  when 
that  with  the  less  decimation  is  in  fixation  a  divergence  occurs. 

If  also,  as  it  sometimes  happens,  there  is  little  or  no  declination 
for  one  eye  with  great  declination  for  the  other,  we  have  the  impor- 
tant elements  of  intermittent  strabismus.  If  the  eye  with  little  or  no 
declination  is  in  fixation,  there  may  be  no  deviation  of  the  eyes,  but 
if  that  with  the  extreme  declination  is  the  fixing  eye,  strabismus 
occurs. 

These  principles  will  be  more  fully  developed  in  the  sections 
on  strabismus. 

We  have  thus  for  the  first  time  a  logical  and  a  uniformly  appli- 
cable explanation  for  all  the  various  forms  of  so-called  concomitant 
strabismus.  With  a  good  understanding  of  the  principles  of  rotation 
and  of  declination  there  is  no  longer  a  necessity  for  a  new  theory  for 
each  form  of  strabismus. 

Without  entering  upon  the  details  of  all  the  elements  inducing 
diverging  squint,  it  may  be  stated  that  there  will  be  found  the  same 
class  of  declinations  in  exotropia  as  are  found  in  exophoria,  but  in 
high  degrees.  So  in  hypertropia  the  conditions  are  similar  to  those 
of  hyperphoria,  but,  as  in  the  cases  of  esotropia  and  exotropia,  these 
conditions  are  extreme  and  usually  combined  with  anomalies  of  the 
vertical  rotations. 

It  is  not  to  be  assumed  from  the  foregoing  remarks  that  all  the 
problems  of  heterotropia  are  to  be  solved  by  any  single  class  of  phe- 
nomena or  by  any  single  rule. 


LOCAL  SYMPTOMS  OF  DECLINATIONS. 

Many  of  the  symptoms  of  declinations  are  similar  to  or  the  same 
as  those  which  are  attributed  to  heterophoria.  But  since  the  study 
of  the  former  class  of  anomalies  has  placed  the  whole  subject  of 
heterophoria  in  a  new  light  a  considerable  number  of  the  symptoms 
which  appeared  to  result  from  heterophoria  can  now  be  directly  asso- 


250  ANOMALIES  OF  MOTOR  MUSCLES. 

ciated  with  the  definite  disturbing  cause  as  it  was  not  possible  to  do 
before. 

One  of  the  most  common  and  persistent  of  the  local  symptoms 
is  dryness  of  the  eyelids  with  smarting  of  the  eyes  and  a  sensation 
of  grit  in  them.  The  chronic  hypergemia  of  the  lids  which  is  so 
annoying  to  many  patients  and  so  difficult  to  cure  is  in  most  cases  the 
direct  result  of  the  pressure  of  the  lids  against  the  eyeball,  a  pressure 
exerted  to  hold  the  eyes  steady  in  resisting  the  tendency  to  roll  inci- 
dent to  the  inclination  of  the  meridians.  The  hypergemia  disappears 
without  direct  treatment  when  the  declination  is  corrected.  I  have 
elsewhere1  shown  the  importance  of  the  condition  of  anophoria  as  an 
Eetiological  element  of  trachoma,  and  this  condition  is  the  more  im- 
portant in  its  ffitiological  effects  in  proportion  as  it  is  complicated 
with  pronounced  leanings  of  the  meridians. 

Another  symptom,  less  local,  is  the  habitual  pain  in  and  over 
the  brow  of  one  eye  or  those  of  both  eyes.  If  the  brows  are  carefully 
observed,  it  does  not  require  minute  inspection  to  see  that  one  or 
both  brows  are  strongly  arched,  or  that  one  brow  is  flattened  against 
the  eye  while  the  other  is  arched.  Above  the  arching  brow  there  are 
to  be  seen  in  many  cases  folds  in  the  skin  showing  the  tension  of 
muscles  beneath. 

The  pain  above  the  brow  in  these  cases  is  not  a  reflex  disturbance, 
but  the  immediate  and  legitimate  suffering  of  the  musc.es  acting  to 
elevate  or  depress  the  brow.  This  is  shown  when  the  declination  is 
relieved,  for  the  brows  then  at  once  assume  a  gentle  curve  and  the 
pain  vanishes  in  a  day. 

It  will  be  found  that  with  myopia  there  is  uniformly  a  high 
'degree  of  declination  and  when  the  pressure  of  the  torsional  muscles 
about  the  eyeball  is  considered  it  is  evident  that  with  such  pressure 
combined  with  a  plastic  state  of  the  sclera,  a  state  which  may  easily 
result  from  the  disturbed  nutrition  of  the  eyeball  when  heterophoria 
exists,  the  globe  from  ordinary  mechanical  laws  might  become  elon- 
gated. One  of  the  strong  expressional  signs  of  a  high  degree  of 
declination  is  a  prominence  of  the  eyeball,  a  more  or  less  goggled 
appearance,  and  it  is  well  known  that  this  is  a  condition  largely 
characteristic  of  myopia.  It  arises  from  the  forward  pull  of  the 
obliques. 


1  "British  Medical  Association,  1897."      Published  in  Ophthalmic  Review,. 
September,  1897. 


ASTIGMATISM  AND  MYOPIA.  251 

Quite  in  contrast  with  this,  but  from  corresponding  but  not 
identical  conditions  of  declination,  is  the  state  of  the  eyes  in  which 
they  appear  to  be  placed  in  very  close  proximity  to  each  other.  This 
closeness  of  the  eyes  to  each  other  is,  like  the  contrasting  condition 
of  prominence,  a  result  of  certain  forms  of  declination,  and  often 
exists  even  when  there  is  a  high  grade  of  exophoria. 

ASTIGMATISM  AND  MYOPIA. 

It  not  unfrequently  happens  that  after  a  correction  of  declina- 
tion a  preexisting  astigmatism  disappears  or  is  modified  in  degree 
or  direction.  So  frequently  have  such  modifications  been  observed 
from  a  correction  of  declination  that  for  a  number  of  years,  in  cases 
in  which  I  am  treating  declinations,  I  reserve  the  prescription  for 
cylindrical  glasses  in  astigmatic  cases  until  after  the  declination 
treatment  is  finished.  I  called  attention  to  the  fact  that  a  loss  of  the 
normal  sphericity  of  the  globe  (astigmatism)  is  a  legitimate  result 
of  adjustments,  in  which  the  muscles  which  surround  the  eye  like 
a  band  are  held  at  abnormal  tension,  in  an  article  on  declination  in 
Archives  of  Ophthalmology,,  No.  1,  1899.  The  statement  was  based, 
not  only  on  theoretical  but  on  practical  grounds,  for  I  had  not  un- 
frequently seen  the  astigmatism  greatly  modified  by  declination 
operations  previous  to  the  publication  of  that  article. 

In  the  same  article  I  also  spoke  of  the  elongation  of  the  eyeball 
in  myopia  as  the  result  of  similar  but  more  uniform  pressure  of 
these  encircling  muscles.  I  added :  "It  may  well  be  thought  that 
the  constant  pressure  brought  to  bear  by  both  the  oblique  and  straight 
muscles  in  marked  cases  of  declination  may  influence  the  form  of  the 
globe,  but  there  must  be  a  combination  of  circumstances  to  induce 
such  a  result. 

"In  the  first  place  the  scleral  walls  must  be  in  a  plastic  con- 
dition. Such  a  condition  may  be  one  of  the  reactions  from  the  ten- 
sions of  heterophoria.  A  reddening  of  the  conjunctiva  or  of  the 
borders  of  the  lids  very  frequently  tells  of  the  tensions  of  hetero- 
phoria, and  the  sclera  may  suffer  a  change  of  nutrition  in  the  same 
way.  When  the  eye  is  in  this  plastic  state  and  the  tension  of  the 
muscles  which  encircle  it  is  too  great,  there  is  every  reason  to  expect 
the  eye  to  yield  to  the  pressure.  Myopia  is  a  progressive  disease.  If 
with  the  first  indications  of  the  elongation  of  the  globe,  the  condi- 
tions which  induce  hypersmia  and  which  cause  unfavorable  pressure 


252  ANOMALIES  OF  MOTOR  MUSCLES. 

are  removed,  a  very  rational  expectation  may  be  entertained  that  the 
further  progress  of  the  elongation  of  the  globe  may  be  arrested. 

"One  of  the  most  characteristic  local  effects  of  declinations  is 
the  amblyopia  which  is  in  many  cases  associated  with  it.  Such 
amblyopias  are  found  in  high  degrees  of  heterophoria,  in  strabismus, 
and  in  high  grades  of  astigmatism.  It  is  probable  that  even  in  these 
states  the  defective  vision  is  to  be  attributed  in  large  degree  to  the 
declinations." 

Under  the  heading  "Unconscious  Conclusions"  (Section  XYIII) 
attention  has  already  been  called  to  the  interesting  phenomena  of 
aberration  of  the  color  sense  and  of  the  muscular  and  locomotive  sense 
resulting  from  heterophoria,  but  principally  from  declinations.  It 
is  usually  the  eye  in  which  the  declination  is  most  pronounced  that 
attributes  the  deepest  color  to  an  identical  object,  and  it  is  with  ex- 
tremely high  degrees  of  declination  which,  however,  the  person  is  able 
in  great  measure  to  control,  that  the  uncertainty  of  locomotion  occurs. 

DECLINATIONS,  THE  CONTOUR  OF  THE  BROWS  AND  THE  EELATIVE 
POSITIONS  OF  THE  EYES. 

This  leads  to  a  part  of  the  subject  which,  while  in  the  line  of 
the  discussion,  passes  from  the  domain  of  painful  affections  to  that 
of  facial  expressions.  From  that  point  of  view  it  will  be  more  fully 
discussed  in  the  section  devoted  to  that  subject.  So  important,  how- 
ever, are  these  expressions  in  their  practical  relations  to  declina- 
tions that  a  brief  summary  of  the  most  conspicuous  should  find  a 
place  here.  The  scope  of  this  section  does  not  permit  of  more  than 
a  mention  of  a  few  of  the  peculiarities  in  the  contour  and  the  sym- 
metry or  asymmetry  of  the  two  brows.  The  subject  when  consid- 
ered in  all  its  bearings  is  most  interesting,  but  it  will  serve  the  present 
purpose  to  mention  three  of  the  most  conspicuous  forms  of  expression 
about  the  brows  which  are  in  direct  relation  to  the  declinations  of 
the  meridians.  So  characteristic  are  these  that  when  either  is  con- 
spicuously present  it  is  easy,  not  only  to  recognize  the  class  of  declina- 
tions, but  to  tell  the  direction  of  the  leaning  of  each  eye. 

In  the  form  in  which  both  brows  slant  or  arch  upward  from  the 
temples  toward  the  median  line,  the  internal  extremity  ending  al- 
most in  the  general  direction  of  the  line  of  slant  or  suddenly  curving 
down  at  the  inner  end  as  it  is  seen  in  the  diagram  (Fig.  117,  page 
321),  we  may  look  for  positive  declinations  for  both  eyes  and  of 


CONTOUR    OF  BROWS   AND   DECLINATION.  253 

nearly  the  same  extent.  It  is  an  expression  which,  some  years  ago, 
I  associated  with  exophoria,  but  the  more  recent  observations  show 
that  not  only  the  expression  but  the  exophoria  itself  has  its  cause  in 
the  direction  of  the  meridians. 

A  second  form  of  direction  of  the  brows  which  is  also  most  fre- 
quently associated  with  exophoria,  but  which  is  sometimes  found 
with  esophoria,  is  that  in  which  each  of  the  brows  ascends  from  the 
inner  extremity  outward,  forming  what  I  have  called  "the  bird's 
wings"  eyebrows  (Fig.  118,  page  322).  Here  the  declination  is  posi- 
tive for  each  eye,  but  the  extent  of  the  declination  differs  materially 
in  the  two  eyes.  Such  a  declination  may,  when  the  positive  declina- 
tion is  quite  moderate  in  one  eye  and  is  more  decided  in  the  other, 
give  rise  to  esophoria,  but  the  nearer  the  approach  to  equality  of 
declination  in  the  two  eyes  the  greater  the  probability  of  exophoria 
resulting. 

Again,  the  position  of  the  brows  assumes  the  directions  shown 
in  the  diagram  (Fig.  114,  page  319).  The  diagram  here  appears 
somewhat  extravagant,  but  it  is  a  common  form  of  expression,  and 
a  close  observer  will  soon  find  that  it  is  by  no  means  exaggerated. 
It  is  a  form  of  expression  Avhich  indicates  homonymous  declination 
with  the  positive  leaning  at  the  side  with  the  compressed  brow  and 
the  negative  leaning  at  the  side  on  which  the  brow  rises  toward  the 
temple.  One  of  the  common  modifications  of  this  form  is  that  in 
which  both  brows  curve  strongly,  but  one  is  drawn  much  farther 
upward  than  the  other. 

Associated  with  these  asymmetrical  or  anomalous  positions  of 
the  brows  are  frequently  found  asymmetrical  positions  of  the  eye- 
balls. Thus,  for  example,  with  a  marked  depression  of  one  of  the 
brows  there  is  frequently  found  a  depression  of  the  position  of  the 
whole  eyeball,  and  in  some  cases  of  double  pressure  of  the  brows 
both  eyes  are  dislodged  downward.  (See  Figs.  115  and  116,  page 
321.) 

It  is  interesting  to  remark  that  it  is,  in  the  great  majority  of 
cases,  the  left  brow  that  is  depressed,  and  this  is  in  accord  with  the 
fact  that  in  practice  a  great  majority  of  cases  of  positive  (  +  )  de- 
clinations are  found  on  the  left  side.  So  emphatically  is  this  the  rule 
that  in  my  earlier  experience  with  the  clinoscope,  I  was  led  to  very 
frequent  verifications  of  the  position  of  the  test  lines  of  the  instru- 
ment, since  the  preponderance  of  such  cases  seemed  quite  improbable. 
Several  years  of  constant  use  of  the  cMnoscope,  however,  has  left  no 


254  ANOMALIES  OF  MOTOR  MUSCLES. 

doubt  that  positive  declination  is  by  far  most  frequently  found  in  the 
left  eye. 

What  may  be  the  essential  reason  for  this  I  do  not  attempt  to 
explain,  but  a  suggestion  may  not  be  inappropriate.  The  great  ma- 
jority of  people  are  not  only  right-handed,  but  they  have  inherited 
right-handedness.  It  is  known  that  the  left  cerebral  lobe  is  usually, 
almost  invariably,  larger  than  the  right.  May  it  not  happen  that 
with  the  unequal  development  of  the  brain  the  bony  walls  of  the 
orbits  are  molded  in  conformity  with  this  unequal  cerebral  develop- 
ment? And  if  this  be  true,  is  it  not  a  forcible  argument  against 
forcing  children  to  use  one  hand  to  the  neglect  of  the  other?  The 
inheritance  may  not  fail  in  the  first  generation,  but  at  least  some 
approach  to  symmetrical  brains  and  symmetrical  orbits  may  be  hoped 
for  even  in  one  generation. 


POSE  OF  THE  HEAD  FROM  DECLINATION". 

The  habitual  pose  of  the  head  and,  indeed,  that  of  the  body 
are  in  a  large  measure  influenced,  it  might  be  said  controlled,  by 
peculiarities  in  the  normal  adjustments  of  the  eyes.  Independent  of 
the  position  of  the  normal  plane  of  vision,  which  has  an  important 
controlling  influence  upon  the  pose  of  the  head  and  body,  when  there 
exists  a  positive  (  +  )  declination  for  each  eye  the  head  is,  in  many 
cases,  thrown  backward  as  it  is  when  the  plane  of  vision  is  low.  This 
high  carriage  of  the  head  is  commonly  associated  with  chronic  pains 
at  the  base  of  the  skull,  at  a  point  over  the  spine  of  the  seventh 
cervical  vertebra  and  at  points  between  the  shoulder-blades  or  just 
below  each  scapular  angle,  with  habitual  aching  in  the  lumbar  region. 
If,  in  these  cases,  the  plane  of  vision  is  raised  where  it  was  originally 
low,  or  if  the  positive  declination,  when  it  exists,  is  corrected,  the 
head  is  no  longer  habitually  thrown  backward,  the  back  no  longer 
bends  in,  the  tension  is  removed  from  the  muscles,  and  relief  from 
the  pain  is  experienced. 

When  the  declination  is  toward  one  side  or  confined  to  one  eye 
it  assumes,  in  extreme  cases,  a  cause  of  drawing  of  the  head  toward 
that  side,  and  where  the  drawing  of  the  head  to  the  side  is  great, 
chronic  spasm  of  the  muscles  of  the  neck  may  result.  A  number  of . 
extreme  and  long-continued  cases  of  torticollis  have  yielded  to  the 
treatment  directed  exclusively  to  these  anomalies  of  declinations. 


GENERAL   SYMPTOMS    OF   DECLINATION.  255 


OTHER  SYMPTOMS. 

Vertigo  is  one  of  the  symptoms  so  closely  related  to  declinations 
that  it  may  be  said  that,  in  general,  vertigo  is  the  direct,  not  the 
reflex,  effect  of  the  declinations.  Carried  to  its  extreme  manifesta- 
tion, the  vertiginous  attack  becomes  epileptoid,  and  without  doubt 
the  underlying  principle  in  both  vertigo  and  true  epilepsy  is  the 
same. 

The  more  recent  experiences  with  ocular  causes  of  epilepsy — and 
beyond  a  doubt  a  great  proportion  of  idiopathic  cases  of  epilepsy 
have  for  their  cause  ocular  conditions — show  that  when  we  arrive 
at  the  root  of  the  matter  the  declinations  are  the  most  important  if 
not  the  essential  of  these  ocular  elements.  The  relief  which  often 
follows  correction  of  the  refractive  errors  or  the  anomalies  of  hetero- 
phoria  may  probably  be  due  largely  to  the  fact  that  with  the  greater 
freedom  of  action  of  the  adjustments  of  the  eyes  and  the  consequent 
relief  from  fatigue  the  management  of  the  declinations  becomes  less 
difficult  and  disturbing.  If  we  proceed  directly  to  correct  the  anom- 
alous declinations,  the  results  upon  the  epileptic  state  are  much  more 
certain  and  more  quickly  and  permanently  marked  than  when  the 
heterophoric  conditions  are  alone  treated.  Whatever  the  theory  may 
be,  the  fact  is  that  in  many  cases  in  which  the  correction  of  refrac- 
tive and  heterophoric  anomalies  only  modifies  the  epileptic  state  a 
correction  of  declinations  serves  to  arrest  the  epileptic  seizures.1 

Space  does  not  allow  of  any  extended  mention  of  insomnia,  dys- 
pepsia, mental  disturbances,  and  many  other  forms  of  nervous  reac- 
tions which  in  very  frequent  instances  have  their  origin  in  the  class 
of  defects  under  consideration,  and  it  is  needless  to  attempt  to  intro- 
duce a  catalogue  of  reactions  which  may  be  induced  by  this  defect, 
but  it  may  be  said,  in  a  general  way,  that  many  of  the  nervous  reac- 
tions which  result  from  heterophoria  may  also  have  their  origin  in 
the  normal  tiltings  of  the  meridians.  Enough  has  been  said  to  indi- 
cate that  declinations  are  important  elements  of  nervous  irregulari- 
ties, and  if  that  is  established  it  follows  that  the  forms  of  manifesta- 
tion? may  be  numerous  and  varied. 


1  The  so-called  "Jacksonian  Epilepsy"  is,  in  fact,  not  epilepsy — it  is  a 
convi^sive  disease  dependent  upon  gross  lesions  of  the  nervous  centers  and 
should  not  be  classed  with  an  affection  which  is  conceded  to  have  no  recog- 
nizable pathology. 


256  ANOMALIES  OF  MOTOR  MUSCLES. 

TREATMENT  OF  DECLINATIONS. 

While,  under  certain  circumstances,  glasses,  spherical,  cylin- 
drical, or  prismatic,  may  and  doubtless  do  have  an  influence  in  in- 
ducing or  in  correcting  declinations  of  the  images  of  objects,  no 
practical  and  systematic  use  of  lenses  can  be  made  in  the  treatment 
of  this  class  of  anomalies.  It  is  only  important  in  this  connection 
to  remark  that  decimation  of  the  images  (not  of  the  eyes)  is  easily 
induced  by  a  bad  adjustment  of  strong  lenses,  and  that  the  greater 
care  which  is  observed  in  the  adjustment  of  glasses  in  recent  over  not 
very  remote  times  is  even  more  important  than  it  is  generally  sup- 
posed. 

There  is  little  doubt  that  the  influence  of  strong  convex  glasses 
in  temporarily  modifying  or  even  apparently  correcting  some  cases 
of  converging  strabismus  while  the  glasses  are  before  the  eyes,  is  due 
to  the  fact  that  with  such  glasses  the  eyes  are  able  to  find  a  position 
in  which  the  deflection  of  the  image  induced  by  the  glass  in  some 
measure  neutralizes  the  declination  of  the  eye.  When  this  important 
function  is  added  to  the  prismatic  action  which  may  also  be  selected 
by  the  eyes  in  the  interest  of  a  correction  of  hyperphoria  we  have 
perhaps  found  a  full  explanation  of  the  effect  of  convex  glasses  on 
strabismus.  The  effect  of  such  glasses  is  certainly  not  in  the  relief 
to  the  ciliary  muscles. 

Naturally,  when  the  subject  of  declination  is  exercising  the  func- 
tions of  adjustment  of  the  eyes  excessively,  or  when  the  nervous 
energy  is  insufficient  for  the  demand  upon  it,  there  is  liable  to  result 
more  of  the  local  or  more  general  unpleasant  effects  of  declination 
than  when  the  subject  of  the  defect  is  under  more  favorable  condi- 
tions. Hence  rest,  abundance  of  fresh  air,  relief  from  work  demand- 
ing continued  and  difficult  adjustments  of  the  eyes  with  agreeable 
environments  are  means  by  which  some  or  possibly  all  the  injurious 
effects  of  declination  may  be  for  the  time  modified,  and  if  to  these 
means  we  add  a  correction  of  refractive  errors  by  glasses  and  the  use 
of  tonics,  we  have  summed  up  the  principle,  if  not  all  the  means  at 
our  disposal,  for  the  relief  from  the  effect  of  declination  short  of  a 
radical  removal  of  the  defect  itself,  which  can  only  be  accomplished 
by  surgical  interference.  In  another  place  reference  to  gymnastic 
exercises  in  cases  of  declination  will  be  made.  Naturally,  such  gym- 
nastics are  not  in  any  sense  curative. 


ACCOMMODATIVE  AXIAL  ADJUSTMENTS.  257 

As  it  will  be  found  most  convenient  to  devote  a  section  to  the 
subject  of  surgical  operations  on  the  ocular  muscles,  the  reader  is 
referred  to  that  section  for  the  "Surgical  Treatment  of  Declinations." 


SECTION  XXIX. 

ACCOMMODATIVE  AXIAL  ADJUSTMENTS. 

Class  III. 

The  affections  of  the  ocular  muscles  included  in  this  are  physio- 
logical peculiarities  rather  than  affections  arising  from  pathological 
conditions. 

It  is  unquestionable  that  the  conditions  of  Classes  I  and  II  have 
much  to  do  in  inducing  some  if  not  most  of  the  affections  of  this 
class,  and  the  three  classes  cannot  therefore  be  regarded  as  inde- 
pendent of  each  other.  For  while  the  conditions  in  Class  I  or  Class 
II  are  perhaps  always  primary,  it  has  been  shown  that  at  least  a 
part  of  those  now  to  be  discussed  are  secondary. 

In  the  normal  adjustments  of  the  eyes  of  most  persons  in  early 
life  in  the  act  of  vision,  two  distinct  classes  of  muscles  perform  each 
its  distinct  and  separate  office.  The  muscle  of  accommodation,  situ- 
ated within  the  eyeball,  acts  as  the  focal  adjuster  for  each  eye,  while 
the  long  muscles  within  the  orbit  direct  the  eyeballs  in  such  a  way 
as  to  bring  the  visual  axes  of  the  two  eyes  to  bear  upon  the  point  for 
which  the  focal  adjustment  is  made. 

These  two  classes  of  muscles,  although  independent  of  each  other, 
are,  during  at  least  some  periods  of  life,  in  somewhat  close  synergic 
relation.  In  a  discussion  of  the  anomalies  of  the  ocular  muscles, 
therefore,  the  relations  between  these  two  classes  should  be  considered. 

This  is  the  more  necessary  since,  according  to  the  view  which 
has  been  almost  universally  entertained  by  ophthalmologists  since 
the  notable  series  of  articles,  commencing  in  I860,1  culminated  in 
the  monumental  work  of  Bonders  on  the  refraction  and  accommoda- 
tion of  the  eye,  these  relations  have  been  regarded  as  the  cause  of 
the  principal  forms  of  strabismus. 

The  view  that  the  association  of  these  two  functions  is  so  essen- 


'  Arch.  far.  Ophthal.,  Bd.  6,  1,  1860. 

17 


258  ANOMALIES  OF  MOTOR  MUSCLES. 

tial  and  so  commanding  that  from  the  excess  of  the  action  of  one 
should  arise  an  excess  in  the  function  of  the  other,  and  that  thereby 
an  anomaly  in  the  functions  of  accommodation  becomes  logically  the 
essential  aetiological  factor  of  the  deviation  in  converging  strabismus, 
has  become  too  generally  accepted  to  be  overlooked. 

It  is  some  years  since  I  have  expressed  my  dissent  from  this 
accepted  view,1  and  I  am  sure  that  we  shall  find  that  it  is  not  only 
unnecessary,  but  illogical.  For  the  line  of  thought  that  leads  to  this 
conclusion  the  reader  is  referred  to  the  section  on  Converging  Stra- 
bismus. 

That  the  associations  of  the  accommodative  and  adjusting  mus- 
cles are  those  arising  from  custom,  and  that  they  may  be  interrupted 
at  any  time,  is  a  matter  of  daily  observation. 

If  we  examine  stereoscopic  diagrams  in  which  the  effect  of  relief 
is  induced,  we  have  the  effects  of  different  degrees  of  convergence, 
while  the  accommodation  remains  stationary.  This  very  simple  illus- 
tration of  the  ease  with  which  the  two  functions  are  disassociated  is 
but  one  of  a  great  number. 

The  affections  of  the  ciliary  muscles,  therefore,  are  not  essential 
factors  of  the  anomalies  of  the  motor  muscles,  and  need  not  be  con- 
sidered in  this  connection  beyond  the  reciprocal  influences  which  may 
arise  from  habitual  associations. 


SECTION  XXX. 

DIFFERENCE  OF  DEGREE  OF  ANOMALOUS  CONDITIONS  OF 
THE  MOTOR  MUSCLES. 

In  the  classification  adopted  it  appears  that  the  anomalies  of 
the  directing  muscular  apparatus  of  the  eyes  are  divided  into  two 
main  groups:  first,  those  which  permit  of  habitual  binocular  vision; 
second,  those  in  which  a  blending  of  the  images  of  the  two  eyes  is 
so  difficult  as  to  be,  in  most  instances,  impossible.  In  the  first  of 
these  groups  binocular  vision  is  maintained  by  the  expenditure  of  a 
greater  amount  of  force  than  is  demanded  in  perfect  equilibrium  of 
the  ocular  muscles;  in  the  second  the  amount  of  force  demanded  is 


1  British  Medical  Association,  1894;  International  Ophthalmological  Con- 
gress, 1894. 


DIFFERENCE  OF  DEGREE  OF  ANOMALIES.  259 

usually  greater  than  can  be  continuously  supplied.  There  are,  .how- 
ever, cases  belonging  to  this  class  (and  it  is  probable  that  they 
constitute  the  majority)  in  which  it  is  not  so  much  a  question  of 
amount  of  force  as  a  question  of  ability  to  arrange  the  elements  of 
force  so  as  to  act  with  each  other  in  producing  the  desired  end — 
binocular  vision.  Such  cases  may  occur  with  extravagantly  high 
rotations  or  with  important  declinations. 

The  two  classes  are  therefore,  in  general,  different  degrees  of 
similar  affections,  the  classification  depending  upon  the  psychical 
presence  or  absence  of  the  phenomenon  of  fusion  of  images.  Under 
certain  circumstances  the  conditions  of  one  of  these  groups  may  pass 
into  the  other.  One  who  in  robust  health  blends  images  habitually 
and  without  conscious  difficulty,  may,  in  a  condition  of  impaired 
nervous  energy,  be  quite  unable  to  maintain  a  fusion  of  the  images 
of  the  two  eyes. 

Even  the  presence  of  or  the  absence  of  binocular  vision,  then, 
does  not  constitute  an  absolute  and  sharply  denned  line  of  classifica- 
tion. 

It  happens  also  that,  with  gross  departure  from  the  standard  of 
equilibrium  of  the  eye  muscles,  habitual  binocular  vision  is  some- 
times maintained.  It  depends  largely  upon  the  combinations  of 
anomalous  conditions.  One  might,  in  case  of  a  tendency  of  the  eyes 
to  deviate  in,  for  example,  under  circumstances  of  moderate  leaning 
of  the  meridians,  maintain  the  fusion  of  the  images,  but  should  this 
be  accompanied  by  a  tilting  of  the  vertical  meridian  of  a  more  con- 
siderable extent,  the  fusion  might  no  longer  be  possible.  Hence,  it 
could  not  be  said  that  at  n  degrees  of  deviating  tendency  esophoria 
must  become  esotropia. 

With  an  increased  difficulty  in  adjusting  a  declination,  a  very 
slight  degree  of  esophoria  might  become  esotropia. 

The  boundary  lines  for  the  sustained  pressure  of  single  vision 
are  then,  like  many  other  boundaries  of  classification  in  science,  some- 
what extensible,  yet  they  will  be  found,  on  the  whole,  practical  and 
satisfactory. 

As  we  direct  our  attention  to  the  first  group  of  anomalies,  that 
in  which  single  vision,  is  habitually  maintained,  we  find  a  field  of 
observation  rich  in  interest  and  of  preeminent  importance  in  its 
practical  bearing. 


260  ANOMALIES  OF  MOTOR  MUSCLES. 

SECTION  XXXI. 

EQUILIBRIUM. 

In  a  system  like  this  the  term  equilibrium  should  signify  a  con- 
dition in  which  all  the  muscles  of  the  two  eyes  are  so  proportioned 
and  adjusted  in  respect  to  their  dynamic  conditions  that  with  the 
least  expenditure  of  nervous  energy,  when  the  gaze  is  directed  to  an 
object  in  the  median  plane  at  the  level  of  the  eye  and  at  infinite  dis- 
tance while  the  head  is  in  the  primary  position,  the  visual  lines  should 
be  parallel  and  in  the  same  horizontal  plane.  In  turning  from  this 
position  to  any  other  they  should  come  to  the  new  position  in  exact 
conformity  with  the  Law  of  Listing. 

This,  when  the  normal  plane  of  vision  is  too  high  or  too  low  or 
when  marked  declination  exists,  does  not  automatically  occur.  The 
torsions  are  disproportioned  to  the  extent  of  the  ascensional  (or 
decensional)  angle  and  the  lateral  displacements,  and  hence  the 
visual  lines  do  not  under  such  circumstances  unite  at  the  point  in- 
tended without  an  impulse  of  the  will,  which  is  beyond  what  we  may 
for  convenience  term  the  automatic  effort.  A  condition  of  positive 
equilibrium  then  would  involve  the  most  favorable  normal  plane  of 
vision,  an  absence  of  declination  and  parallelism  of  the  visual  lines 
under  the  conditions  stated. 

The  terminology  to  be  employed  in  the  discussion  of  the  con- 
ditions in  the  second  division  of  this  classification  do  not  relate 
exclusively  to  this  condition  of  absolute  equilibrium,  but  to  that 
equilibrium  which  may  be  found  when  associated  with  various  ad- 
justments of  the  plane  of  vision  or  of  the  meridians.  Thus,  ortho- 
phoria  may  exist,  notwithstanding  the  presence  of  anophoria  or  de- 
clination. 


SECTION  XXXII. 

Class  III. 
FIRST  DIVISION. 

Adjustments  of  the  Directing  Muscles  of  the  Two  Eyes  by  Which 
the  Two  Visual  Lines  May  Be  and  Are  so  Controlled  that  Binocular 
Vision  is  Habitually  Maintained. 


ORTHOPHORIA  AND   HETEROPHORIA.  261 

I.  ORTHOPHORIA. 

The  term  is  applied  to  the  visual  lines,  and  means  that  these 
lines  are,  for  a  given  plane,  in  a  state  of  typical  adjustment  for  that 
plane.  They  neither  have  a  tendency  to  approach  nor  to  recede  from 
each  other,  nor  does  one  have  a  tendency  to  rise  above  or  to  fall 
below  the  other. 

All  this,  however,  is  only  when  the  minimum  impulse  is  sent 
along  the  nerves  governing  these  movements. 

Orthophoria,  then,  while  indicating  the  best  adjustment  in  the 
plane  in  which  we  find  the  eyes,  may  not  be  the  ideal  adjustment  when 
the  question  of  anophoria,  katophoria,  or  declination  is  taken  into 
consideration. 


SECTION  XXXIII. 

HETEROPHORIA. 

From  what  has  been  said  in  the  section  devoted  to  "Declination" 
it  is  evident  that  various  conditions  of  heterophoria  may  manifest 
themselves  as  the  result  of  the  automatic  effort  to  adjust  the  retinal 
meridians  for  the  field  of  view.  As  a  matter  of  fact,  heterophoria 
may  be  regarded  as  in  general  a  resultant  of  declination  and  of  ad- 
justments of  the  eyes  above  or  below  a  certain  plane  relative  to  the 
cranium. 

Accepting  this  view,  it  is  apparent  that  the  various  forms  of 
heterophoria  are  not  such  independent  states  as  to  demand  unquali- 
fied consideration  separate  from  their  causative  conditions. 

Yet,  so  individualized  are  some  of  the  phenomena  of  the  dif- 
ferent forms  of  heterophoria,  that  it  is  convenient  and  advisable  to 
study  these  phenomena  in  relation  with  each  form.  Hence,  if  these 
forms  are  isolated  for  convenience  of  study,  it  must  be  borne  in 
mind  that  they  are  always,  in  practice,  to  be  associated  with  the 
underlying  conditions. 

The  term  heterophoria,  indicating  an  absence  of  the  ideal  ad- 
justments in  a  given  plane,  is  naturally  antithetical  to  the  term 
orthophoria.  In  heterophoria  there  exists  a  tendency  or  tendencies 
unfavorable  to  the  adjustments  of  the  eyes  in  perfect  accord.  There 
is  power  to  hold  the  two  eyes  in  such  relation  that  single  vision  is 
habitually  maintained,  but  the  tendency  is  for  the  visual  lines  to 


262  ANOMALIES  OF  MOTOR  MUSCLES. 

drift  out  of  their  proper  relations.  It  is  therefore  by  an  effort  of 
the  will,  conscious  or  unconscious,  that  they  are  forbidden  thus  to 
drift.  Even  at  the  expense  of  a  good  deal  of  automatic  effort,  single 
vision  may  be  maintained.  This  tendency  on  the  part  of  the  visual 
lines  to  deviate  from  the  legitimate  path,  but  which  can  be  restrained, 
must  not  be  confounded  with  the  unrestrained  deviation  which  results 
in  actual  strabismus. 

There  is  in  the  tendencies  of  heterophoria  no  actual  turning  of 
one  or  other  of  the  visual  lines  in  directions  not  corresponding  with 
the  point  of  fixation.  In  gazing  directly  forward  at  a  distant  object 
parallelism  is  supposed. 

There  is,  however,  on  the  part  of  one  or  more  muscles  a  ten- 
dency to  disturb  this  balance,  and  should  the  nervous  control  be 
removed  so  as  to  permit  of  the  consummation  of  this  tendency,  an 
actual  deviation  would  result. 

Such  irregular  tendencies  may  exist  in  as  many  directions  as 
there  are  forces  to  induce  irregular  tension — that  is,  not  only  in  as 
many  directions  as  there  are  muscles  to  act,  but  in  as  many  directions 
as  the  muscles  may  combine  to  act.  In  short,  the  tendencies  of 
heterophoria  may  exist  in  all  directions. 

Without  stopping  here  to  discuss  the  question  whether  it  is  im- 
portant to  discover  all  these  tendencies  and  to  determine  as  far  as 
possible  their  extent — a  subject  which  will  occupy  our  attention  as 
we  advance — we  may  here  assume  that  all  are  important,  and  that 
no  just  appreciation  of  the  conditions  which  induce  asthenopic  or 
kindred  troubles  can  be  acquired  which  does  not  take  them  all  into 
account. 

It  becomes  necessary,  then,  to  establish  some  methodical  course 
of  investigating  and  of  recording  such  anomalies. 

As  long  as  "insufficiency  of  the  interni"  was  the  objective  end 
of  the  investigation  there  was  no  uniform  custom  or  rule  for  exam- 
ining in  relation  to  that  condition  either  as  to  the  distance  at  which 
the  test  object  should  be  placed  or  as  to  the  exact  character  of  the 
condition  which  might  be  found,  unless  the  dot  and  line  test  of  von 
Graefe  should  be  so  considered.  Beside  the  dot  and  line  test,  von 
Graefe  used  a  prism  held  in  the  hand  while  the  patient  looked  at  an 
object  six  feet  distant,  or  he  caused  the  patient  to  look  at  a  pencil, 
his  finger,  etc.,  and  as  the  object  approached  the  eyes  he  observed 
the  distance  at  which  one  eye  deviated  out  while  the  other  remained 
in  fixation. 


PRINCIPLES   OF  EXAMINATION.  263 

Still  another  method  was  that  of  passing  a  screen  from  one  eye 
to  the  other,  concealing  the  image  alternately  of  one  and  the  other 
eye,  while  the  examiner  observed  whether  the  eye  released  from  the 
screen  was  forced  to  move  in  for  fixation. 

When,  by  the  prism  and  dot  and  line  test,  the  degree  of  "insuffi- 
ciency" was  determined,  it  was  advised  to  examine  the  abduction  at 
a  greater  distance.  Von  Graefe  did  not  specify  the  distance,  but 
mentions  his  experience  in  abduction  and  adduction  at  a  distance  of 
six  feet. 

SECTION  XXXIV. 
PRINCIPLES  OF  EXAMINATIONS  IN  HETEROPHORIA. 

The  manner  in  which  the  faulty  conditions  of  heterophoria  may 
be  detected  was  shown  by  myself  in  connection  with  the  classification 
above  mentioned.1 

In  order  that  in  what  is  to  follow  there  be  no  confusion  from 
the  use  of  instruments  in  which  there  are  any  complications,  the 
simplest  possible  methods  will  in  this  introductory  section  be  em- 
ployed. The  imperfection  of  such  methods  may  for  the  time  be 
overlooked  until  the  principles  are  mastered,  when  more  accurate 
practical  methods  must  take  the  place  of  those  used  here  tentatively. 

Position  of  the  Person  Examined. — The  head  is  to  be  in  the 
primary  position,  the  body,  sitting  or  standing,  preferably  the  former, 
erect,  without  crossing  of  the  knees  or  any  bodily  restraint.  The  body 
should  be  perfectly  free.  The  test  object,  which  may  be  the  flame 
of  a  candle  or  other  bright  point  not  too  large,  should  be  not  less 
than  twenty  feet  in  front  of  the  observer  in  the  median  line  and  at 
the  height  of  the  eyes. 

Tests  by  Diplopia. — Whatever  objections  there  may  be  to  the, 
use  of  the  diplopia  tests  they  are  practically  the  only  tests  upon 
which  reliance  can  be  placed. 

The  theory  of  the  tests  by  diplopia  rests  upon  the  ground  that 
when  single  vision  becomes  impossible  the  voluntary  efforts  for  ad- 
justment will  be  abandoned,  and  it  is  assumed  that  the  visual  lines 
will  adjust  themselves  in  the  directions  and  mutual  relations  which 
would  exist  if  the  minimum  of  nervous  impulse  were  acting  upon 
them. 

'Page  215. 


264  ANOMALIES  OF  MOTOR  MUSCLES. 

This  theory  is  not  entirely  correct  and,  indeed,  may  under  cer- 
tain circumstances  be  very  far  from  correct.  The  means  of  guard- 
ing against  errors  from  the  method  will  engage  our  attention  as  we 
proceed. 

The  test  object  (flame  of  candle,  bright  spot,  etc.)  should  be 
seen  against  a  dark  background  and  one  on  which  are  no  marks  or 
figures  by  which  the  eyes  are  helped  to  form  a  judgment  concerning 
the  vertical  or  horizontal  planes.  Such  lines  as  oculists  have  some- 
times introduced  about  the  test  object,  in  order  that  the  patient  may 
answer  positively,  defeat  the  object  of  the  test. 

Diplopia  may  be  caused  by  a  prism  which  will  be  so  strong  that 
the  effort  to  unite  images  will  be  abandoned  but  not  so  strong  as  to 
remove  the  images  too  far. 

Let  diplopia  be  first  induced  in  the  vertical  direction.  If  the 
prism  is  placed  with  its  base  down  before  the  right  eye  the  image  of 


Fig.  102. 

the  candle  flame  seen  by  that  eye  will  be  elevated  above  the  other, 
since  the  action  of  the  prism  will  be  to  deflect  the  beam  of  light 
downward  toward  the  base  of  the  prism  and  the  image  will  conse- 
quently appear  at  a  position  higher  than  that  which  it  really  occu- 
pies, while  the  image  of  the  other  candle  will  remain  as  before. 

If  the  eye  fixes  the  candle  flame  through  the  prism  at  c  (Fig. 
102),  the  ray  ac  is  deflected  downward  as  it  traverses  the  prism  at  c, 
and  the  image  of  the  flame  is  not  seen  in  the  direction  ac,  but  in  the 
direction  of  the  deflected  ray,  and  will  appear  in  the  direction  cb. 

If,  the  eyes  being  released  from  the  necessity  of  holding  the 
visual  lines  in  parallel  directions,  the  visual  lines  now  take  the  direc- 
tion which  is  most  easy  and  natural,  one  of  three  things  will  happen : 
The  image  of  the  right  eye  will  appear  exactly  in  a  vertical  line  above 
the  other,  or  it  will  deviate  to  the  right  or  deviate  to  the  left  of  the 
other.  It  may  indeed  do  more  than  this.  If  the  object  is  an  erect  one, 
like  a  candle,  it  may  appear  to  lean,  or  it  may  appear  in  advance  of 
the  lower  flame  or  bevond  it. 


PRINCIPLES   OF  EXAMINATION.  265 

What  are  the  indications  of  these  various  phenomena?  The 
inquiry  will  for  the  present  be  limited  to  the  first  three  bearings  above 
mentioned. 

When  the  image  of  the  upper  flame  is  seen  exactly  above  the 
other  it  means  that  the  impression  is  received  at  a  point  of  the  retina 
lower  than  that  at  which  the  impression  of  the  left  flame  is  received, 
but  in  the  corresponding  vertical  meridian  of  each  eye.  In  other 
words,  although  the  eye  has  been  given  an  opportunity  to  swing  to 
the  right  or  to  the  left,  it  has  not  improved  that  opportunity.  Had 
we  placed  behind  the  flame  a  vertical  white  line  by  which  the  judg- 
ment would  have  been  corrected,  the  act  of  the  will  would,  to  some 
extent  at  least,  have  exerted  an  influence  to  bring  the  upper  flame 
into  line.  As  no  such  mental  aid  has  been  rendered,  we  may  assume 
that,  owing  to  the  fact  that  the  laterally  acting  muscles  of  the  two 
eyes  are  closely  in  equilibrium,  the  nervous  impulse  which  directs  the 


Fig.  103. 

left  eye  to  a  given  point  in  the  horizontal  plane  is  exactly  sufficient 
to  direct  the  right  to  a  precisely  corresponding  point  in  its  horizon. 
There  is  found  no  tendency  on  the  part  of  the  eyes  to  vary  from 
parallelism. 

K^ext,  suppose  that  the  image  of  the  right  eye  has  deviated  to 
the  right.  In  this  case  some  relative  change  in  the  position  of  the 
eye  has  taken  place.  If  the  image  is  seen  at  the  right  of  the  other  its 
impression  is  received  at  a  vertical  meridian  at  the  left  of  the  macula 
of  the  right  eye,  assuming  that  the  left  image  continues  to  be  seen 
at  the  macula  of  that  eye.  If  in  the  figure  (Fig.  103)  the  image  of  f 
falls  at  the  macula  m,  the  image  seen  at  the  point  TO'  at  the  left  of 
the  macula  would  appear  at  /'  or  at  the  right  of  the  image  /.  Diplopia 
Avhen  it  occurs  in  this  relation,  that  is,  when  the  image  seen  by  the 
rjght  eye  is  seen  at  the  right  side  and  that  seen  by  the  left  eye  is  located 
at  the  left  side,  is  known  as  homonymous  diplopia  (homonymous — 
having  the  same  name).  Whether,  in  our  experiment,  the  left  eye 
continues  to  fix  the  image  at  the  macula  while  the  image  of  the  right 


266  ANOMALIES  OF  MOTOR  MUSCLES. 

is  received  at  a  different  meridian,  or  whether  both  images  are  some- 
what displaced,  is  not,  in  this  connection,  a  question  of  any  practical 
importance,  but  for  the  sake  of  the  illustration  we  say  assume  that 
the  right  image  drifts.  This  homonymous  diplopia  then  would  mean, 
on  this  assumption,  that  the  point  m  of  the  figure  had  slipped  to  the 
left  to  occupy  the  position  of  the  point  in'.  The  eye  has  rotated  in 
or  toward  the  left. 

Hence,  when  the  double  images  are  homonymous  under  the  cir- 
cumstances of  our  examination,  the  visual  lines  are  no  longer  parallel, 
but  approach  each  other. 

This  deviation  of  the  visual  lines  toward  each  other  can  be 
measured.  If  a  prism  is  placed  before  either  the  left  eye,  which  is 
supposed  to  be  directed  to  the  exact  position  of  the  flame,  or  before 
the  right,  which  has  already  the  vertical  prism  before  it,  the  image 
may  be  deflected  to  the  right  or  left  if  the  prism  has  its  base  at  the 
side.  To  measure  the  deviation  of  homonymous  images  the  measur- 
ing prism  must  have  its  base  out,  or  in  the  direction  of  the  temple. 

By  trying  one  prism  after  another,  the  one  which  brings  the  two 
images  to  an  exact  vertical  line  is  chosen  as  that  which  measures  the 
deviation  inward,  for  it  is  this  prism  which  causes  the  beam  of  light 
to  deflect  to  the  right  just  far  enough  to  reach  the  meridian  of  the 
macula.  Hence  the  deviation  under  these  circumstances  may  be  said 
to  be  2°,  4°,  etc.,  of  prism.  As  a  degree  (or  diopter)  of  prism  causes 
a  deflection  of  about  i/G0  of  arc,  the  actual  deviation  of  the  lines  then 
in  the  case  of  4°  would  be  about  2°  of  arc. 

Such  a  deviation  is  not  to  be  recorded,  as  it  has  often  been  in 
print,  as  2°  or  4°  of  homonymous  diplopia.  The  diplopia  was  first 
formed  by  the  vertical  prism,  and  the  deviation  under  the  circum- 
stances represents  the  deviating  tendency  and  not  an  actual  diplopia 
when  no  prism  is  interposed. 

Had  the  image  seen  by  the  right  eye,  the  higher,  in  the  original 
experiment,  appeared  at  the  left,  there  would  have  been  a  crossing 
of  the  images,  and  heteronymous  deviation  would  have  been  present. 

This  would  have  signified  that  the  image  of  the  flame  caused  an 
impression  on  the  right  retina  at  a  vertical  meridian  at  the  right  of 
the  macula.  Turning  to  Fig.  103  it  will  be  seen  that  in  order  to  d/> 
this  the  eye  would  have  to  turn  to  the  right,  that  is,  the  visual  axis 
of  this  eye  would  deviate  outward  from  the  left.  As  in  the  first 
instance,  it  is  unnecessary  to  inquire  whether,  as  a  fact,  the  right 


PRINCIPLES   OF  EXAMINATION.  267 

eye  only  deviates,,  or  whether  the  deviation  is  divided.  Our  attention 
is  directed  for  the  present  to  the  right  eye. 

As  the  point  at  which  the  impression  is  made  is  at  the  right  of 
the  macula,  the  amount  of  turning  out  of  the  axis  may,  as  before, 
be  measured  by  a  prism  which  will  deflect  the  light  toward  the  left. 
That  is,  by  a  prism  with  its  base  in. 

This,  in  regard  to  the  three  conditions  mentioned,  is  what  may 
be  learned  by  causing  diplopia  in  the  vertical  direction. 

Let  the  experiment  be  varied  by  placing  before  the  right  eye  a 
prism  with  its  base  exactly  at  right  angles  to  the  horizon.  If  it  is 
with  the  base  out  or  toward  the  temple  the  eyes  will  in  most  cases 
make  such  an  adjustment  as  to  unite  the  images,  unless  the  prism  is 
of  very  high  refracting  power,  and  so  many  elements  of  error  may 
result  that  it  is  better  to  try  the  other  way.  Placing  it  with  the  base 
toward  the  nose,  in,  a  prism  of  moderate  degree  will  in  the  majority 
of  cases  overcome  the  efforts  to  unite  and  diplopia  will  result. 

This  time,  if  the  prism  is  held  correctly  and  the  ocular  adjust- 
ments are  perfect,  the  images  will  appear  in  a  horizontal  line.  The 
prism  deflects  the  light  toward  the  nasal  side  of  the  retina  and 
homonymous  diplopia  is  induced. 

Recurring  to  the  theory  that,  the  necessity  for  maintaining  par- 
allelism having  been  interrupted,  the  eye  will  drift  where  it  is  most 
agreeable,  that  is,  to  the  place  of  minimum  tension,  if  the  images 
remain  horizontal,  it  is  because  the  image  of  the  right  eye  has  been 
deflected  outward  directly  along  the  horizontal  meridian  of  the  retina, 
which  passes  through  the  macula.  Had  there  been  a  tendency  on  the 
part  of  one  eye  to  permit  the  visual  line  to  drift  above  or  below  the 
other  visual  line,  evidence  would  have  been  present  that  in  respect  to 
directing  the  eyes  horizontally  there  was  a  want  of  equilibrium.  It 
would  mean  that  the  tensions  of  the  vertically  acting  muscles  of  the 
two  eyes  are  unequal,  but  it  would  not  prove  that  the  eye  which  re- 
mains the  highest  is  really  too  high,  nor  would  it  even  suggest  that 
the  superior  or  the  inferior  rectus  of  one  or  the  other  eye  is  "insuffi- 
cient" to  perform  its  function  perfectly.  It  may  be  entirely  a  ques- 
tion of  declination. 

It  will  be  found  as  we  advance  that  as  a  matter  of  fact  when 
there  is  paresis  or  weakness  of  one  of  the  elevating  muscles  or  de- 
pressing muscles  diplopia  will  usually  be  accompanied  by  the  phe- 
nomenon of  images  at  unequal  heights,  but  the  question  of  paresis 
or  of  weakness  must  be  determined  in  quite  another  manner. 


268  ANOMALIES  OF  MOTOR  MUSCLES. 

If,  in  the  experiment,  the  image  of  the  right  eye  (which  in  this 
case  would  be  the  right  image)  appears  lower  than  the  other,  it  is 
hecause  the  impression  is  made  at  a  point  in  the  retina  situated  on  a 
horizontal  meridian  higher  than  the  macula  (we  are  adhering  to  the 
supposition,  no  matter  whether  correct  or  not,  that  the  image  changes 
position  only  in  the  eye  hefore  which  the  prism  is  placed).  If  we 
examine  the  same  diagram  (Fig.  103)  it  will  appear  why  the  image 
of  the  right  is  be'ow. 

If  the  image  is  at  /_,  hut  is  seen  at  /'  or  below,  then  the  image 
does  not  fall  upon  the  macula,  but  at  a  point  in  a  horizontal  plane 
above  the  macula.  But,  since  the  line  connecting  the  object,  the 
nodal  point  and  the  macula  must  be  a  straight  line  (the  deflection 
caused  by  the  prism  being  here  neglected),  the  point  m  must  occupy 
the  position  in'.  Hence,  the  axis  of  this  eye  will  in  fact  be  directed 
upward. 

From  this  it  may  be  concluded  that,  in  the  experiment,  the  lowest 
image  belongs  to  the  eye  whose  axis  points  highest.  When  the  image 
of  the  right  eye  is  above,  the  axis  of  this  eye  points  below  the  other; 
when  lowest,  it  points  above  the  other. 

The  measurement  of  this  deviation  may  be  made  as  in  case  of 
the  previous  experiment.  If  the  image  is  low  (and  the  impression 
high)  the  prism  which  will  just  correct  the  position  of  the  impression 
by  bringing  it  down  to  the  meridian  of  the  macula  will  be  the  measure 
of  the  deviation. 

By  these  two  experiments  may  be  found  the  tendencies  of  the 
visual  lines  to  drift  toward  each  other,  away  from  each  other,  or  to 
assume  different  relations  to  the  horizontal  plane,  and  by  combining 
the  results,  the  different  elements  of  an  oblique  tendency  may  be 
determined. 

It  remains  to  make  brief  mention  of  two  other  classes  of  phe- 
nomena which  may  be  found  by  inducing  diplopia  in  this  manner. 

When  the  two  images  are  separated  either  in  the  horizontal  or 
vertical  direction,  if  they  are  the  images  of  an  erect  linear  object, 
they  may  not  be  parallel.  If,  for  example,  a  candle  is  used  for  the 
object,  and  if  diplopia  is  induced  by  the  horizontal  prism,  the  images 
may  appear  to  lean  toward  each  other  at  the  top  or  to  lean  away  from 
each  other.  In  the  first  instance  there  is  evidence  that  the  vertical 
meridian  of  one  or  of  both  eyes  leans  out  at  the  top,  for  the  apparent 
leaning  of  the  image  will  be  exactly  opposite  to  the  real  leaning  of 
the  meridian  of  the  eye. 


PRINCIPLES   OF  EXAMINATION.  269 

This  phenomenon  belongs  to  the  subject  of  declinations,  and  the 
reader  is  referred  to  the  section  devoted  to  that  topic  for  more  de- 
tailed discussion.  Still  another  phenomenon  requires  attention.  The 
images  in  case  of  such  diplopia  as  is  made  in  our  experiment  with 
the  prism  (page  264)  do  not  always  appear  at  equal  distances.  Sup- 
pose that  the  image  of  the  right  eye  appears  more  distant  than  the 
other  and  more  distant  than  it  is  in  reality. 

This  brings  us  somewhat  beyond  the  realm  of  physiological  optics 
in  which  we  have  thus  far  found  the  answer  to  our  inquiries,  into 
that  of  physiological  psychology. 

The  distance  of  the  object  in  this  case  is  measured  mentally  by 
the  muscular  effort  demanded  in  the  adjustment,  and  this  leads  to 
the  fact  that,  notwithstanding  the  theoretical  passiveness  of  adjust- 
ments of  the  e}res  in  the  experiments,  there  remains  an  element  of 
muscular  tension.  The  consciousness  of  where  an  image  ought  to  be 
is  extremely  potent  and  does  not  surrender  on  slight  inducement. 
The  ordinary  experience  of  the  individual  is  here  brought  into  requi- 
sition. In  general,  when  we  look  at  near  objects  the  plane  of  regard 
is  depressed.  This  is  not,  of  course,  always  so.  If  we  look  at  the 
faces  of  our  friends  they  are  in  the  plane  of  our  eyes.  But,  in  gen- 
eral, it  is  not  the  case  that  a  near  object  is  at  the  level  of  the  eye. 
If  we  walk  upon  the  seashore  we  look  down  upon  the  breaker  which 
rolls  in  from  the  sea.  But  we  elevate  the  gaze  to  see  the  ship  at  the 
horizon.  Hence  the  sensation  of  lifting  the  eyes  becomes  associated 
with  the  idea  of  distance.  Now  in  the  experiment,  if  the  observer, 
in  the  instinctive  effort  to  bring  the  images  to  a  horizontal  plane 
exerts  some  force  to  raise  one  of  the  eyes  while  none  or  comparatively 
less  is  exerted  in  that  direction  by  the  other,  the  image  of  this  eye 
appears  more  distant  than  the  other.  Beyond  this  is  the  effect  of 
torsions,  which  occur  in  looking  down  with  convergence,  but  which 
may  in  certain  cases  of  hyperphoria  be  so  modified  as  to  become  an 
important  element  in  the  illusion  of  apparent  comparative  distance. 


270  ANOMALIES  OF  MOTOR  MUSCLES. 

SECTION  XXXV. 

SIGNIFICANCE  OF  HETEROPHORIC  CONDITIONS.1 

We  have  already  seen  that  the  ideas  of  space,  of  form,  and  of 
depth  as  acquired  through  the  visual  sense  are  derived  from  the  mus- 
cular sense,  and  therefore  from  the  actions  almost  exclusively  of  the 
muscles  which  move  the  eyes.  We  have  also  seen  (Section  XXIV) 
that  the  retinal  spaces  which  may  hecome  the  measures  of  these 
movements  are  not  only  often  minute  and  never  large,  but  that  corre- 
sponding retinal  spaces  must  mark  corresponding  movements  of  the 
two  eyes. 

In  order  to  see  clearly,  a  perfect  horopter  must  be  formed,  and 
to  form  a  perfect  horopter,  perfect  adjustments  of  the  two  eyes,  not 
only  in  respect  to  the  directions  of  the  visual  lines,  but  in  respect  to 
the  relative  positions  of  the  meridians,  must  he  induced  and  main- 
tained. 

When  it  is  considered  that  this  marvelous  accuracy  of  estimation 
of  the  muscular  movements  of  the  two  eyes  must  be  brought  into 
continuous  requisition  so  long  as  the  mind  takes  cognizance  of  objects 
through  the  visual  sense,  and  that  these  infinitely  nice  adjustments 
must  be  made  in  numberless  directions  and  positions  with  a  rapidity 
which  is,  paradoxical  as  the  expression  may  appear,  quicker  than 
thought,  it  must  become  evident  that  the  question  of  the  comparative- 
ease  and  perfection  with  which  these  movements  can  be  made,  and, 
in  fact,  are  made,  assumes  a  position  of  great  practical  importance. 
If,  writh  every  glance  and  during  all  the  hours  that  the  visual  func- 
tion is  exercised,  this  demand  for  exact  estimations  of  energy  ex- 
pended and  this  nice  comparison  of  the  relative  energy  directed  to 
each  eye  is  never  for  an  instant  relinquished,  it  is  evident  that  it 
cannot  require  very  gross  impediments  in  the  way  of  the  free  action 
of  these  delicate  muscles  nor  very  considerable  faults  in  the  associa- 
tions of  movements  to  induce  disturbance  of  nervous  actions  which 
may  reach  to  the  highest  degree. 

We  may  not  be  able  to  assume  that,  with  a  certain  degree  of  fault 
in  the  associated  movements,  a  certain  form  or  degree  of  nervous 
disturbance  must  follow. 


xThe  principles  applying  to  heterophoria  in  this  section  are  equally 
applicable  to  declinations  and  anomalies  of  the  adjustments  of  the  eyes  for  the 
plane  of  vision. 


TIME  FOR  ATTENDING  TO  ANOMALIES.  271 

The  native  force  at  the  disposal  of  the  individual,  the  environ- 
ments in  which  he  may  be  placed,  the  character  of  the  demands  made 
upon  the  adjusting  and  measuring  faculties  of  the  eyes,  the  demands 
made  upon  the  nervous  forces  in  other  directions,  are  some  of  the 
elements  to  determine  the  reactions  which  must  follow  the  disad- 
vantageous use  of  the  eyes  when  any  of  the  anomalous  conditions  of 
heterophoria  are  present. 

Hence,  it  must  happen  that  conditions  of  heterophoria  which  are 
apparently  little  disturbing  in  one  person  may  induce  most  important 
disturbances  in  another  person.  The  same  individual  who,  if  occu- 
pied in  the  open  air  and  engaged  only  in  looking  at  objects  in  a  very 
general  way,  may  be  quite  free  from  any  reactions  from  heterophoria, 
will  perhaps  become  the  victim  of  some  severe  neurosis  if  he  is  obliged 
to  remain  in-doors  and  devote  himself  to  steady  work  requiring  exact 
and  continuous  use  of  the  eyes.  The  fact,  then,  that  one  may  have 
experienced  no  inconvenience  from  the  use  of  the  eyes  may  not  signify 
that  there  is  a  well  balanced  adjustment  of  the  muscles. 

A  difference  in  surroundings,  the  demands  for  unusual  hours  of 
work,  as  in  attending  upon  the  sick,  or  the  depressed  state  of  the  nerv- 
ous forces  after  an  illness,  may  reveal  the  fault  which  was  not  before 
recognized. 

SECTION  XXXVI. 

THE  TIME  FOR  ATTENDING  TO  THE  ANOMALIES  OF  HETEROPHORIA. 

The  question  when  the  anomalous  conditions  of  heterophoria 
should  receive  attention  is  one  of  importance.  Should  one  wait  until 
some  special  form  of  suffering  leads  to  the  conclusion  that  the  eyes 
are  at  fault  before  giving  them  relief?1 

Even  in  the  conditions  which  have  been  mentioned  in  which  by 
virtue  of  surplus  energy  and  favorable  environments  the  effects  of 
heterophoria  are  not  observed,  it  is  evident  that  the  cost  to  the  nerv- 
ous system  of  adjusting  the  eyes  when  heterophoria  exists  is  greater 
than  it  would  be  with  orthophoria.  Other  things  being  equal,  the 
person  with  orthophoria  would  be  able  to  accomplish  more  work  de- 
manding the  expenditure  of  nervous  energy  than  the  person  with 
some  form  of  heterophoria.  That  a  vast  number  of  children  fall 


1  As  in  the  last  section,  the  principles  applied  to  heterophoria  are  also 
applicable  to  decimations,  anophoria  and  katophoria. 


272  ANOMALIES  OF  MOTOR  MUSCLES. 

behind  in  studies  because  of  such  faults,  although  there  may  be  no 
local  manifestation  of  discomfort  from  the  use  of  the  eyes,  cannot 
be  doubted.  In  the  race  for  precedence  in  which  all  at  the  present 
time  are  so  earnestly  engaged,  the  necessity  for  the  removal  of  every 
handicap  is  evident. 

Of  two  boys  or  of  two  girls  of  equal  native  abilities,  of  equal 
physical  force  and  of  equal  advantages,  the  boy  or  the  girl  with 
orthophoria  is  destined  to  outstrip  his  or  her  companion  who  is  the 
subject  of  heterophoria. 

This  being  the  case,  is  it  best  to  wait  until  the  mischief  is  accom- 
plished ? 

There  is  no  more  important  principle  in  medicine  than  that  it 
is  better  to  prevent  than  to  heal  a  disease. 

Hence,  the  self-evident  answer  is  that  every  boy  or  girl  on  enter- 
ing school  is  fairly  entitled  to  be  examined  in  this  respect,  and  that 
if  any  fault  is  found,  such  provision  as  is  best  calculated  to  reduce 
the  disadvantage  to  its  lowest  degree  should  be  made. 


SECTIOX  XXXVII. 

SPECIFIC  METHODS  AND  INSTRUMENTS  FOR  EXAMINATIONS  IN 
HETEROPHORIA. 

In  the  discussion  of  the  general  principles  of  examinations  in 
heterophoria  it  was  found  that  the  deviating  tendencies  might  be 
shown  by  inducing  diplopia  by  means  of  a  prism. 

This  method  is  subject  to  several  objections,  some  of  them  of 
great  importance.  It  is  only  necessary  to  mention  that  it  is  difficult 
to  determine  when  the  head  is  exactly  in  the  primary  position  and 
when  the  prism  is  held  exactly  so  as  to  refract  in  a  certain  direction. 
Most  important  is  the  fact  that  when  a  prism  or  any  instrument  for 
determining  heterophoria  is  held  near  the  eye  there  is  a  strong 
tendency  on  the  part  of  the  eyes  to  neutralize  the  effect  by  adjust- 
ments of  abduction,  adduction,  or  sursumduction.1 

In  view  of  these  and  other  sources  of  error,  I  devised,  in  1888, 


1  This  subject  has  been  discussed  by  the  author  somewhat  at  length  in 
the  Ophthalmic  Record,  January,  1892. 


THE  PHOROMETER. 


273 


the  phorometer,  in  which  the  aim  was  to  combine  the  greatest  sim- 
plicity with  the  greatest  attainable  accuracy. 

By  means  of  this  instrument  may  be  made  the  most  reliable  tests 
which  at  present  we  are  able  to  make,  and  the  information  gained  is 
more  uniform  and  the  different  facts  obtained  are  more  in  harmony 
with  each  other  than  when  examinations  are  made  by  other  methods. 

THE  PHOROMETER. 

The  phorometer  consists  of  a  standard  and  adjustable  arm  and 
a  slide  with  rotating  prisms.1  (Figs.  104  and  105.) 


Fig.  104. — Author's  Phorometer. 


The  standard  is  supported  by  a  tripod  and  is  extensible.  At  the 
upper  extremity  is  an  endless  screw  locking  an  arc  by  which  motion 
is  communicated  to  the  arm.  The  arm,  directly  over  the  standard, 


1  The  phorometer  was  described  in  the  Medical  Record,  May  5,  1888.  It 
had,  however,  been  publicly  used  and  exhibited  several  months  prior  to  this 
publication. 


274 


ANOMALIES  OF  MOTOR  MUSCLES. 


is  furnished  with  a  spirit  level.  A  slide  containing  two  cells  (Fig. 
105)  is  so  attached  to  the  arm  that  it  can  be  moved  to  any  part  of  it. 
In  each  cell  rotates  a  disc  and  each  disc  carries  a  prism  of  5°.  Each 
disc  is  furnished  with  a  border  of  cogs,  and  a  small  gear  wheel  placed 
between  the  two  discs  communicates  movement  from  one  disc  to  the 
other.  A  raised  band  around  the  outer  border  of  each  cell  has  a 
scale  of  degrees  or  diopters  increasing  from  the  center  each  way 
from  0°  to  8°,  the  numbers  representing  the  refracting  power  of 
prisms  in  diopters.  The  scale  represents  a  greater  degree  of  accu- 
racy and  uniformity  in  the  refraction  of  prisms  than  is  found  in 


Fig.   105. — Author's  Improved  Rotating  Prism  Slide. 


most  of  the  trial  cases  in  common  use.  By  working  the  handle  which 
is  attached  to  one  of  the  cells  the  two  prisms  are  rotated  in  different 
directions;  that  is,  if  the  edge  of  the  right  prism  is  caused  to  turn 
down,  the  edge  of  the  left  turns  up,  etc.  The  letters,  K.H.,  L.H., 
Es.,  and  Ex.  indicate  the  direction  of  the  pointer  when  right  or  left 
hyperphoria,  esophoria,  or  exophoria  is  found. 

Directions  for  Using  the  Phorometer. — In  using  the  phorometer 
the  instrument  is  placed  before  the  patient  to  be  examined  and  always 
somewhat  removed  from  the  eyes.  A  distance  of  from  four  to  six 
inches  between  the  eyes  and  the  slide  is  sufficient  to  permit  of  some 
freedom  in  respect  to  the  movements  of  the  head,  and  to  insure 
against  the  natural  inclination  to  neutralize  the  indications  of  hetero- 


THE  PHOROMETER.  275 

phoria  which  is  always  present  when  the  instrument  for  testing  is 
held  close  to  the  eyes. 

By  raising  or  lowering  the  upper  part  of  the  standard  the  arm 
is  brought  to  such  a  height  that  the  patient,  with  the  head  as  nearly 
as  is  convenient  in  the  primary  position,  can  look  through  the  glasses 
toward  an  object,  preferably  the  flame  of  a  candle,  situated  at  a  dis- 
tance of  twenty  feet  and  at  the  height  of  the  eyes.  The  slide  with 
the  prisms  will  then  be  so  placed  that  the  side  on  which  are  the  letters 
and  the  scales  will  be  from  the  patient.  The  end  of  the  slide  marked 
E.H.  and  L.H.  will  then  be  before  the  right  eye  of  the  patient,  and 
that  marked  Es.  and  Ex.  will  be  before  the  left  eye. 

Before  making  the  examination  the  arm  should  be  brought  to  a 
perfect  level  by  means  of  the  screw,  as  shown  by  the  spirit  level. 

If  the  examination  is  to  be  made  with  reference  to  the  horizontal 
position  of  the  images,  the  handle  of  the  slide  is  brought  to  the  up- 
right position  and  the  pointer  to  the  0°  mark  at  the  right  side.  The 
prisms  are  then  absolutely  level  with  their  bases  in,  and  homonymous 
diplopia  is  induced  unless  the  eyes  are  able  by  abduction  to  over- 
come the  prisms.  This  may  be  done  in  cases  of  rather  high  degree 
of  exophoria,  and  it  then  becomes  necessary  to  supplement  the  re- 
fracting power  of  the  prisms  by  the  addition  of  another  prism. 

The  slide  with  the  prisms  (Fig.  105)  is  provided  with  a  little 
shelf  or  with  a  slot  behind  the  prisms,  and  an  extra  prism,  cut  square 
and  very  exact  as  to  its  axis,  may  be  slipped  behind  one  of  the  rotat- 
ing prisms.  It  is  well  to  be  provided  with  about  three  such  square 
prisms,  one  each  of  4°,  of  6°,  and  of  8°.  These  will  serve  for  almost 
any  emergency  for  one  or  two  of  these  additional  prisms  will  prevent 
the  union  of  images.  If  they  still  unite  we  are  dealing  with  a  rather 
high  degree  of  strabismus  and  not  with  heterophoria. 

Having  then  induced  homonymous  diplopia,  the  next  step  is  to 
ascertain  whether  the  two  images  are  absolutely  in  the  same  horizontal 
plane. 

If  the  candle  is  in  a  part  of  the  room  otherwise  only  feebly 
lighted,  it  is  an  advantage  and  all  casings,  shelves,  or  other  objects 
which  may  assist  the  patient  in  correcting  his  notions  as  to  the  hori- 
zon should,  as  far  as  possible,  be  absent.  The  practice  which  some 
have  adopted,  of  drawing  horizontal  and  vertical  lines  behind  the 
object  (the  candle),  is  thoroughly  bad,  since  the  impulse  to  correct 
a  difference  in  height  of  the  images  or  a  difference  laterally  becomes 


276  ANOMALIES  OF  MOTOR  MUSCLES. 

so  much  greater  when  such  aids  are  present  that  the  test  is  largely 
and  often  completely  neutralized. 

If  it  is  found  that  one  image  is  higher  than  the  other  the  prisms 
are  rotated  until  the  images  are  level.  By  making  the  last  part  of 
the  rotation  quite  slow  a  higher  degree  of  correction  may  possibly  be 
made  than  if  the  adjustment  is  quickly  made. 

The  pointer  now  marks  the  amount  of  deviation  of  the  images 
from  the  horizontal  plane.  If  the  pointer  is  above  the  0°  point,  it 
indicates  n°  of  right  hyperphoria,  hut  if  below  the  0°  mark,  n°  of 
left  liyperphoria.  It  is  well,  after  the  test  has  been  made,  to  throw 
the  prisms  out  of  position  in  order  to  verify  the  correctness  of  the 
result. 

This  test  being  made  the  lever  is  next  brought  down  rotating 


Fig.  106.— Maddox  Rod. 

the  prisms,  so  that  they  are  adjusted  one  with  base  down,  the  other 
with  base  up.  It  is  now  ascertained  whether  the  two  images  are  in  a 
vertical  line.  If  the  upper  image  is  deflected  to  the  right  the  pointer 
(on  the  left  end  of  the  slide)  will  be  moved  toward  the  letters  Ex.r 
that  is,  downward;  if  toward  the  left  the  pointer  will  move  upward 
toward  the  letters  Es.  The  figures  on  the  margin  will  indicate  the 
degree  of  exophoria  or  esophoria. 

Rod  Test  for  HeteropJioriaJ1 — A  form  of  test  for  heterophoria 
which  has  the  advantage  of  being  convenient,  portable,  and  inex- 
pensive is  the  "rod  test,"  which  consists  of  a  disc  of  metal  or  hard 
rubber  having  the  size  of  a  lens  of  the  trial  case  and  which  holds  in 
the  center  a  glass  rod  (see  Fig.  106).  The  effect  of  the  rod  is  to 
transform  the  flame  of  a  candle  into  a  long  streak  of  light.  The 


E.  H.  Maddox:       Ophthalmic  Review,  May,  1890. 


THE  STEXOPAIC  LENS. 


277 


theory  of  the  rod  test  is,  the  image  of  the  eye  before  which  the  rod 
is  placed  being  so  dissimilar  to  that  of  the  other  eye,  no  effort  will 
be  made  to  bring  these  strongly  contrasting  images  into  union  by  the 
exercise  of  force  in  overcoming  heterophoric  tendencies. 

If  the  line  deviates  from  the  flame  the  prism  which  brings  it 
to  pass  through  the  flame  gives  the  measure  of  the  heterophoria. 
Prisms  from  the  trial  case  are  used  for  these  measurements  as  in  the 
case  of  the  prism  held  in  the  hand. 


Fig.  107.— Author's  Stenopaic  Lens. 

Sievens's  Stenopaic  Lens.1 — This  is  another  test  based  upon  the 
principle  of  contrasting  images.  (Figs.  107  and  108.)  Using  this 
lens,  the  flame  of  a  candle  is  transformed  into  a  large  and  perfectly 
defined  disc  of  diffused  light.  The  principle  of  the  test  is  in  the 
fact  that  if  a  distant  flame  or  point  of  light  is  seen  through  a  very 
strong  convex  glass  the  flame  becomes  a  confused  mass  of  light,  and 
that  if  the  lens  is  then  covered  except  a  very  small  opening,  the  mass 


1 G.   T.   Stevens:      Annales   d'Oculistique,    1892,   and   New   York   Medical 
Journal,  January  16,  1892. 


278 


ANOMALIES  OF  MOTOR  MUSCLES. 


of  light  becomes  a  well-defined  disc,  and  the  prismatic  effort  which 
would  be  induced  by  looking  through  a  point  even  1  millimeter  from 
the  center  is  eliminated. 

The  lens  as  constructed  is  a  disc  of  hard  rubber  of  the  size  of 
the  glasses  of  the  trial  case.  In  the  center  is  set  a  lens  of  13  diopters 
refraction  which  is  seen  only  through  an  opening  less  than  1  milli- 
meter in  diameter.  As  this  is  smaller  than  the  pupil  it  does  not  per- 
mit of  any  deflections  of  the  image  by  prismatic  effect. 

In  orthophoria,  the  flame  of  the  candle  which  is  not  transformed 
is  seen  exactly  in  the  center  of  the  disc  of  light  as  is  shown  in  Fig. 
108  D.  In  heterophoria  the  flame  passes  to  one  side,  above  or  below 
the  center  or  in  a  direction  between  these,  and  may  remain  within  the 
limits  of  the  disc  of  light  or  may  pass  beyond  it. 


Fig.  108. — Form  of  Images  by  the  Author's  Stenopaic  Lens. 

If  the  flame  passes  to  one  side  and  also  rises  above  the  center  or 
falls  below  it,  we  have  all  the  elements  of  the  compound  tendency 
revealed.  (Fig.  108  C.)  The  prism  which  forces  the  flame  back  to 
the  center  of  the  disc  is  the  measure  of  the  deviating  tendency. 

The  disadvantages  of  the  instrument  are  those  common  to  every 
instrument  held  close  to  the  eye  for  making  these  examinations. 

The  theory  that  there  is  an  absence  of  the  impulse  to  force  images 
which  are  contrasting  to  the  macula  of  each  eye  is  not  founded  on 
facts.  Even  the  greatest  contrasts  of  form  or  of  character  of  the 
images  impressed  upon  the  two  retinas  do  not  cause  a  suppression 
of  the  fusion  impulse.  If  one  eye  is  directed  toward  a  strong  point 
of  light,  the  other  eye  will  seek  to  place  the  image  of  the  point,  how- 
ever great  its  change,  upon  the  macula.  Hence  the  tests  of  this  char- 
acter are  unsatisfactory.  Within  very  narrow  limits  the  stenopaic 


AUXILIARY  TESTS.  279 

lens  is  perhaps  one  of  the  most  exact.  So  long  as  the  flame  of  the 
candle  remains  within  the  limits  of  the  halo  there  is  probably  no 
effort  at  abduction,  adduction,  or  sursumduction.  This  appears 
clearly  in  some  cases  of  anisometropia ;  where  one  eye  is  emetropic 
and  the  other  very  myopic  it  will  be  seen  that  the  well-defined  image 
will  swing  up  to  the  very  border  of  the  diffused  one,  but  will  not  pass 
beyond  it.  This  is  because  the  eye  cannot  select  between  different 
parts  of  the  diffused  image,  and  so  long  as  the  outer  border  is  im- 
pressed at  the  macula,  the  demand  for  adjustment  here  is  satisfied. 
The  stenopaic  lens  serves  exactly  this  purpose,  and  its  registration  is 
correct  within  this  narrow  limit,  that  which  cannot  be  said  of  any 
other  test  held  near  the  eye. 

There  are  many  other  important  elements  of  error  than  those 
mentioned  in  all  the  instruments  used  for  inducing  contrasting  im- 
ages. 

Tests  of  HeteropJwria  Auxiliary  to  the  Phorometer. — The  tests 
by  the  phorometer  are  not  absolute.  There  are  other  conditions  which 
must  be  known  in  order  fully  to  understand  the  relative  actions  of 
the  muscles  which  direct  the  movements  of  the  eyes. 

It  therefore  becomes  necessary  to  avail  ourselves  of  every  other 
means  of  ascertaining  their  actual  relations. 

One  of  these  means  is  to  determine  the  ability  of  the  eyes  to 
overcome  difficulties  in  the  fusion  of  images.  This  we  do  by  the 
processes  known  as  abduction,  adduction,  and  sursumduction.  In  each 
case  the  process  is  measured  by  the  strength  of  prism  which  the  eyes 
can  overcome. 

Von  Graefe  called  the  effort  to  unite  images  which  have  been 
separated  by  a  prism  by  rotating  the  eyes  outward,  abduction.1  He 
called  the  effort  to  overcome  the  diplopia  caused  by  prisms  with  the 
bases  out,  and  which  is  accomplished  by  rotating  the  eyes  in,  adduc- 
tion.2 

The  ability  to  overcome  a  prism  with  its  base  up  or  down  before 
one  eye,  has  been  called  by  myself  sursumduction.3 

A  prism  with  the  base  down  before  one  eye  is  equivalent  to  an 
equal  prism  with  its  base  up  before  the  other.  The  effort  made  in 
overcoming  a  prism  with  its  base  down  before  the  right  eye  is  known 
as  right  sursumduction.  A  similar  effort  to  overcome  a  prism  with 


1  Von  Graefe :     Arehiv  f iir  Ophthalmologie,  Bd.  viii,  2. 

2  Von  Graefe :      Op.  cit. 

3  Stevens:       Archives  d'Ophthalmologie,  November,   1886. 


280  ANOMALIES  OF  MOTOR  MUSCLES. 

its  base  down  before  the  left  eye  is  left  sursumduction.1  Naturally 
the  same  terms  apply  if  the  prism  is  reversed  before  the  opposite  eye. 

The  standard  for  abduction  which  I  adopted  many  years  ago  is 
8°  of  prism. 

With  orthophoria  the  great  majority  of  persons  will  accomplish 
this  either  on  the  first  trial  or  after  a  few  trials  on  different  days. 
This  standard  has  been  confirmed  by  many  thousands  of  examinations, 
and  great  experience  has  shown  that  the  ability  to  overcome  a  prism 
with  its  base  in  of  considerably  more  than  this,  or  the  want  of  ability 
to  overcome  one  of  nearly  this  grade,  is  accompanied  generally  with 
other  indications  of  heterophoria,  and  always  with  important  declina- 
tion. 

We  cannot  assume  that  because  there  is  ability  only  to  overcome 
a  prism  of  6°  that  there  is  esophoria  of  2°,  nor  can  we  say  that  there 
is  exophoria  of  4°  because  the  abduction  is  12°.  It  happens  not  un- 
frequently  that  with  an  abduction  of  only  5°  there  is,  as  shown  by 
the  phorometer,  exophoria  of  one  or  more  diopters,  and  with  the 
excessive  abduction  of  12°,  the  phorometer  may  register  5°  or  6° 
esophoria.  While  the  ability  to  overcome  a  verv  strong  prism  with 
its  base  in  may  be  associated  with  actual  converging  strabismus,  and 
while  the  failure  to  overcome  a  comparatively  weak  prism  in  the 
same  direction  may  be  associated  with  an  outward  balance,  these 
irregular  forms  of  abduction  always  indicate  a  complicating  tendency 
which  may  be  and  often  is  in  the  condition  of  hyperphoria,  or  more 
often  it  is  dependent  upon  a  physiological  declination  or  leaning  of 
the  vertical  meridians  of  one  or  of  both  eyes  away  from  the  actual 
vertical  position. 

The  ability  to  overcome  prisms  by  the  act  of  convergence,  that  is, 
uniting  the  images  when  the  bases  of  the  prisms  are  out,  is  known  as 
adduction.  The  ability  in  cases  of  orthophoria  is  about  50°,  but  may 
be  considerably  higher  in  some  cases.  The  ability  may  be  so  greatly 
modified  by  practice  that  an  exact  standard  of  adduction  cannot  be 
stated.  There  is  something  in  acquiring  a  "knack"  of  doing  this 
which  enables  a  person  who  has  acquired  it  to  do  more  than  he  other- 
wise would,  and  there  is  also  a  skill  which  the  surgeon  may  acquire 
by  which  he  can  induce  a  given  person  to  do  very  much  more  than  a 
surgeon  who  has  not  learned  how  to  do  it. 

In  overcoming  prisms  with  the  base  in,  the  grade  of  prism  which 


1  Stevens :      Op.  cit. 


AUXILIARY  TESTS.  281 

can  in  most  cases  be  overcome  is  such  that  it  makes  little  practical 
difference  whether  the  whole  prismatic  effect  is  before  one  eye  or  is 
divided  between  the  two  eyes.  In  adduction,  however,  the  conditions 
are  entirely  different,  and  the  prisms  must  be  as  nearly  as  practicable 
placed  equally  before  the  two  eyes.  Otherwise,  the  free  eye  would 
be  directed  exactly  toward  the  object  while  the  other  would  be  forced 
to  turn  in  to  the  full  extent  of  the  value  of  the  prism. 

The  prism  also  loses  its  effect  long  before  it  reaches  the  full 
ability  of  the  eyes  to  converge,  since  a  prism  passing  45°  has  a  re- 
fracting character  quite  different  from  one  of  less  angle. 

Many  points  of  a  similar  character  may  be  misapprehended  by 
one  who  attempts  to  make  investigations  in  this  field,  unless  all  the 
elements,  not  only  of  a  physiological,  but  of  an  optical  nature  are 
well  considered. 

Should  the  ability  to  overcome  by  adduction  after  a  reasonable 
amount  of  practice  fail  to  reach  50°  of  prism,  it  is  likely  to  be  asso- 
ciated with  either  a  considerable  degree  of  exophoria  or  an  important 
condition  of  hyperphoria,  or  the  images  tilt  as  the  eyes  converge. 

As  a  practical  test  I  many  years  ago  abandoned  the  adducting 
ability  except  in  a  few  cases.  The  value  of  the  practice  of  overcoming 
prisms  is  not  here  in  question. 

The  ability  to  overcome  prisms  with  the  bases  up  or  down,  sur- 
sumduction,  is  in  most  cases  about  2°  of  prism,  but  in  myopia  with 
high  declination  it  is  sometimes  as  high  as  9°,  or  even  more. 

Sursumduction  is,  in  many  cases,  a  valuable  test.  Thus,  one  who 
may  show  little  or  no  hyperphoria  by  the  phorometer  may  show  a 
sursumduction  ability  materially  greater  in  one  direction  than  in 
the  other.  When  this  is  associated  with  a  corresponding  difference 
in  the  upward  rotations,  as  shown  by  the  tropometer,  it  is  evident 
that  the  muscular  adjustment  is  less  satisfactory  than  is  indicated  by 
the  phorometer. 

An  excess  of  sursumduction  leads  to  the  presumption  that  un- 
usual demands  have  been  imposed  on  the  vertically  acting  muscles  in 
maintaining  a  freedom  from  the  effects  of  hyperphoria. 

Sursumduction  ability  may  be  tested  by  placing  a  prism  before 
each  eye  alternately  with  its  base  in  the  same  direction  or  by  placing 
it  before  the  same  eye  with  its  base  alternately  up  and  down.  The 
effect  of  overcoming  a  prism  with  its  base  down  before  one  eye  is  iden- 
tical with  that  for  uniting  with  the  base  up  before  the  other.  Hence, 


282  ANOMALIES  OF  MOTOR  MUSCLES. 

sursumduction  for  both  eyes  may  be  made  with  the  prism  before 
either  eye  by  simply  reversing  it. 

After  testing  sursumduction  in  one  direction,  a  rest  of  a  few 
minutes  should  be  permitted  before  the  trial  in  the  opposite  direction. 

Since  the  introduction  of  the  clinoscope  into  practical  use  non- 
conformity of  the  abduction,  adduction,  and  sursumduction  with  the 
findings  by  the  phorometer  are  in  a  large  measure  explained,  and 
these  collateral  tests  are  less  in  demand  than  formerly,  though  they 
are  not  to  be  ignored. 

Test*  at  Sear  Points. — The  test  which  von  Graefe  employed  in 
his  cases  of  "insufficiency  of  the  interni"  was  made  at  the  near  point 
— the  point  of  reading  of  the  person  examined.  By  a  prism  of  15° 
held  in  the  hand  lie  caused  the  image  of  the  dot  seen  by  one  eye  to 
rise  above  that  seen  by  the  other.  If  the  upper  dot  continued  in  the 
line  there  was  no  insufficiency.  If  it  deviated  from  the  line  so  that 
there  were  not  only  two  dots  but  two  lines,  there  was  "insufficiency" 
equal  to  the  value  of  the  prism  which  would  put  both  dots  in  the 
same  line.  Several  points  are  to  be  considered  in  respect  to  such  a 
test. 

The  great  majority  of  von  Graefe's  cases  of  "insufficiency  of  the 
interni"  were  extremely  myopic  and  had  a  condition  which  he  char- 
acterized as  "latent  strabismus,"  but  which  at  the  present  time  would, 
in  most  instances,  be  regarded  as  actual  diverging  strabismus.  Di- 
verging strabismus  is  less  conspicuous  to  an  observer  than  a  con- 
verging squint  of  the  same  degree. 

A  person  looking  at  an  object  like  the  dot  situated  upon  a  ver- 
tical line  would,  if  vertical  diplopia  were  induced,  make  an  effort 
similar  to  the  effort  of  abduction  or  adduction  to  hold  the  dot  where 
the  line  would  suggest  that  it  should  be.  The  association  of  ideas 
and  of  muscular  action  is  of  the  same  character  as  that  which  induces 
the  effort  to  overcome  prisms. 

In  von  Graefe's  cases  of  moderate  diverging  strabismus  with 
extreme  myopia,  the  effort  to  converge  at  the  very  near  reading  point 
was  one  which  could  not  be  sustained.  The  internal  recti  muscles 
were,  as  he  said,  quite  "insufficient"  for  this  task.  He  did  not  say 
that  they  were  weak,  as  some  have  used  that  term ;  they  were  insuffi- 
cient to  do  a  thing  which  muscles  of  normal  power  could  not  well  do. 

Such  a  test  would  have  no  significance  in  the  cases  known  at 
present  as  exophoria  or  esophoria ;  for  the  impulse  to  hold  the  dot  in 


AUXILIARY  TESTS.  283 

its  proper  line  is  sufficiently  great  to  accomplish  its  purpose  in  a  great 
number  of  anomalous  cases  short  of  actual  strabismus. 

An  exophoria  of  5°  or  6°  or  an  esophoria  of  like  extent  would 
not  necessarily  affect  such  a  test  at  all. 

If  on  the  other  hand  we  remove,  as  far  as  possible,  every  sug- 
gestion of  the  necessity  for  associating  the  two  images  with  any 
particular  direction  we  get  quite  different  results. 

In  general,  with,  for  example,  a  simple  dot  in  the  center  of  a 
pretty  broad  page  held  at  the  distance  of  fifteen  inches,  the  induction 
of  vertical  diplopia  will  be  accompanied  by  a  deviation  of  the  dots 
from  the  vertical  line.  There  is  in  fact  no  reason  except  the  associa- 
tion of  ideas  why  they  should  not  deviate  to  the  extent  of  permitting 
the  visual  lines  to  be  in  the  most  easy  and  natural  position.  If  the 
page  and  dot  should  be  carried,  for  example,  to  the  right  so  that  the 
right  visual  line  would  have  a  direction  parallel  with  the  median 
plane,  and  if  the  prism  were  then  placed  base  down  before  the  left 
eye,  the  images  might  and  would,  except  so  far  as  the  psychological 
association  might  have  an  influence,  deviate  so  that  the  two  visual 
lines  would  be  parallel. 

As  a  matter  of  fact,  the  psychological  element  is  rarely  entirely 
eliminated,  and  a  certain  amount  of  adjustment  almost  always  occurs. 
But  of  the  exact  amount  in  any  individual  case  we  are  unable  to 
predicate. 

Hence  it  must  be  seen  that  a  test  by  vertical  diplopia  at  the 
reading  distance  can  have  no  absolute  value.  It  may  become  a  useful 
collateral  test,  for  should  it  act  in  a  manner  not  in  harmony  with  the 
general  facts  it  might  be,  and  often  is,  suggestive  of  certain  condi- 
tions which  may  not  be  very  apparent  by  other  tests. 

Suppose,  for  example,  that  the  person  examined  should  manifest 
by  the  phorometer  at  the  distance  a  slight  exophoria  and  only  a  frac- 
tion of  a  degree  of  hyperphoria.  If  this  person  were  to  show  a 
marked  convergence  by  the  test  with  vertical  diplopia  at  the  near 
point,  it  would  be  legitimate  to  suppose  that  a  complication  of  mus- 
cular tensions  might  result  from  declination. 

In  practice,  a  person  with  nearly  the  adjustment  of  orthophoria 
will  in  general  show  at  the  near  point  by  such  a  test  (freed  from  all 
suggestive  lines  and  marks)  a  failure  of  convergence  for  the  distance 
of  the  object  of  about  from  4°  to  6°  of  prism. 

It  wi'l  be  seen  then  that  as  a  test  of  the  state  of  the  ocular  mus- 
cles diplopia  of  the  near  point  has  no  direct  value. 


284  ANOMALIES  OF  MOTOR  MUSCLES. 

But  it  will  also  be  seen,  from  what  has  preceded,  that  it  may 
have  a  certain  value  as  a  collateral  test. 

Exophoria  and  Esophoria  in  Accommodation. — In  my  earlier 
writings1  I  attempted  to  make  clear  the  facts  above  stated  and  to 
emphasixe  the  truth  that  diplopia  tests  at  a  distance  induced  by 
prisms  and  those  induced  near  the  eyes  had  not  the  same  meaning. 
In  order  to  distinguish  the  results  of  examinations  made  at  the  two 
points  I  included  in  my  classification  of  conditions  which  might  be 
found,  "esophoria  in  accommodation/'  and  "exophoria  in  accommo- 
dation," the  latter  of  which  was  somewhat  similar  to  the  "insuffi- 
ciency of  the  interni"  of  von  Graefe. 

Generally,  I  think  that  the  radical  distinction  between  "exo- 
phoria'' and  "exophoria  in  accommodation"  was  understood.  Yet 
some  writers  have  interpreted  the  terms  as  meaning  the  same  thing 
discovered  in  different  places. 

In  view  of  such  misunderstanding  it  may  be  a  question  whether 
the  terms  "exophoria  in  accommodation,"  etc.,  were  not  unfortunate. 

In  any  case  it  is  proper  here  to  emphasize  the  fact  that  these 
conditions  found  at  near  points  do  not  represent  the  adjustments 
of  the  eye  muscles.  They  may  vary  from  one  examination  to  another 
to  a  marked  extent.  I  have  seen  reports  of  cure  of  exophoria  by 
exercises  because  the  operator  has  found  less  deviation  one  day  than 
another. 

Deviation  in  Exclusion. — In  certain  cases  of  heterophoria  im- 
portant information  may  be  gained  by  the  method  which  I  have 
called  Deviation  in  Exclusion.  The  method  is  one  which  has  long 
been  used  in  strabismus,  but  the  technique  has  not  until  recently  been 
sufficiently  refined  to  be  suited  to  conditions  of  heterophoria.  In  the 
text-books  the  process  has  been  described  as  passing  the  hand  of  the 
surgeon  before  the  eyes  alternate^. 

The  following  is  the  method  adopted  by  myself  more  than  twenty 
years  ago  and  which  I  have  found  useful  in  many  cases: — 

The  patient,  seated  so  that  a  good  light  falls  upon  the  eyes, 
looks  at  the  flame  of  a  candle  or,  better,  a  spot  on  the  glass  of  a 
window  which  he  faces,  at  twenty  feet  distance  or  somewhat  less. 

The  examiner  sits  in  such  a  position  as  to  be  able  to  observe  even 
the  slightest  perceptible  movement  of  either  eye.  Taking  in  his 
hand  a  small  visiting  card,  the  most  convenient  form  of  a  screen 


1  See  Archives  of  Ophthalmology,  1887,  etc. 


AUXILIARY  TESTS.  285 

which  will  serve  the  purpose  of  excluding  the  distant  object  from 
the  eye  while  permitting  the  surgeon  to  watch  every  movement,  and  a 
screen  which  can  be  passed  so  quickly  that  there  is  no  practical  in- 
terval, he  holds  it  before  one  of  the  eyes,  charging  the  patient  to  look 
intently  at  the  distant  object  and  to  keep  it  clearly  in  sight  at  every 
instant.  The  card  is  then  passed  quickly  before  the  other  eye  and 
the  movement  of  both  eyes  is  closely  observed.  It  is  passed  backward 
and  forward  from  one  eye  to  the  other,  not  too  rapidly  for  the  patient 
to  fix  the  uncovered  eye  each  time  upon  the  object  nor  to  prevent  an 
intelligent  observation  on  the  part  of  the  surgeon. 

If  the  eye  lately  covered  must  make  a  slight  movement  outward 
as  the  card  leaves  it  for  the  other  eye,  it  is  evident  that  behind  the 
screen  it  deviated  inward.  So  if  it  moves  downward  on  being  un- 
covered it  is  evident  that  when  excluded  it  deviated  up. 

We  may  measure  this  deviation  with  a  prism.  Suppose  that  the 
movement  on  removing  the  screen  from  each  of  the  eyes  is  outward. 
A  prism  is  taken  from  the  trial  case  and  held  before  one  eye  with  its 
base  out.  When  the  right  prism  is  reached  the  movement  ceases  and 
the  measure  of  the  apparent  deviation  in  exclusion  is  found. 

But  there  may  be  a  movement  of  adjustment  of  the  eyes  under 
these  circumstances  which  is  so  slight  that  it  may  escape  the  notice 
of  the  surgeon.  If  the  patient  is  quick  in  recognizing  his  own  visual 
perceptions,  he  may  furnish  the  information  which  the  surgeon  could 
not  obtain  by  his  own  eyes. 

This  test,  which  is  quite  delicate  and  often  important,  has  been 
called  by  Dr.  Alexander  Duane  the  parallax  test. 

It  is  made  in  the  manner  described,  but  the  information  is  given 
by  the  patient  who  observes  the  movement  of  the  object.  If  the 
patient  observes  that  the  object  moves  to  the  right  when  the  right 
eye  is  uncovered  and  the  left  is  excluded,  and  to  the  left  when  the 
left  eye  is  uncovered,  it  is  an  indication  of  esophoria.  The  neutraliza- 
tion is  made  by  prisms  until  no  movement  of  the  object  can  be  de- 
tected by  the  patient.  When  the  movement  is  in  an  oblique  direction, 
downward  or  upward  as  well  as  in  a  lateral  direction,  the  prism  is 
held  obliquely. 

This  "deviation  in  exclusion"  does  not  prove  that  the  rotation  of 
the  visual  lines  when  both  eyes  are  used  is  the  same  as  it  is  by  this 
test.  In  fact,  some  quite  pronounced  cases  of  converging  strabismus, 
strabismus  up  to  20°,  will  show  marked  exophoria  by  the  test  of 
deviation  in  exclusion.  In  such  cases,  and  in  many  cases  less  con- 


286  ANOMALIES  OF  MOTOR  MUSCLES. 

spicuously  contradictory  in  this  respect,  the  phenomena  of  the  deviat- 
ing tendency  when  both  lines  of  regard  are  directed  toward  the  object 
are  the  results  of  existing  declinations  of  high  degree. 


SECTION  XXXVIII. 
ESOPHORIA. 

The  condition  of  esophoria  is  that  heterophoric  manifestation 
which  is  most  frequently  encountered.1 

It  is  that  condition  in  which,  while  single  binocular  vision  is 
habitually  maintained,  yet  with  the  nearest  approach  to  the  passive 
condition  which  the  muscular  system  of  the  eyes  is  accustomed  to 
maintain,  the  balance  of  energy  is  such  that  were  the  will  power  com- 
pletely removed  while  all  other  conditions  remained  the  same,  the 
visual  lines  would  converge,  and  the  degree  of  esophoria  would  depend 
upon  the  extent  of  the  approach  of  the  visual  lines  toward  each  other. 

Esophoria,  as  it  will  be  seen  when  the  nature  of  the  condition  is 
discussed,  is  not  to  be  regarded  as  a  disease  or  as  a  weakness,  nor  yet 
as  a  spasm,  although  either  of  these  conditions  may  exist  with  eso- 
phoria. Esophoria  is  a  physiological  state  depending  upon  anatom- 
ical peculiarities  of  the  course  and  of  the  insertions  of  the  motor 
muscles  by  which,  directly  or  more  generally  indirectly,  the  balance 
of  tension  is  normally  toward  the  median  plane. 

The  method  of  determining  esophoria  has  been  indicated  at 
Section  XXXV,  but  will  be  here  stated  more  specifically. 

The  phorometer  being  placed  at  the  distance  of  about  five  or  six 
inches  in  advance  of  the  eyes  and  the  prisms  brought  to  the  vertical 
position,  the  examined  person  directs  the  gaze  toward  a  lighted  candle 
situated  at  a  distance  of  twenty  feet  and  exactly  in  front.  Two  im- 
ages will  appear,  one  of  which  is  higher  than  the  other.  If,  with  the 
phorometer,  the  higher  image  appears  at  the  left  of  the  lower,  the 
lever  causes  the  prisms  to  rotate  so  that  the  pointer  at  the  left  is 
raised  toward  the  symbol  of  esophoria  and  until  the  higher  image 
stands  exactly  above  the  other.  The  pointer,  when  the  images  have 
at  length  settled  in  their  relative  positions,  indicates  the  degree  of 


a Stevens:  Functional  Nervous  Diseases,  p.  267,  1887.  Previous  to  this 
publication  insufficiency  of  the  interni  had  been  regarded  as  the  most  frequent 
even  by  those  who  had  come  to  regard  the  opposite  condition  as  important. 


ESOPHORIA.  287 

manifest  esophoria  as  shown  by  the  figures  at  the  border  of  the  cell. 

If  the  diplopia  has  been  induced  otherwise  than  by  the  phorom- 
eter, and  the  right  image  is  found  at  the  right  of  the  other  and  the 
left  at  the  left,  the  prism  that  brings  one  image  directly  above  the 
other  is  the  measure  of  the  esophoria. 

Such  tests,  with  the  phorometer,  a  vertical  prism,  or  other  device, 
having  been  made,  the  abducting  ability  is  then  to  be  determined. 
The  standard  of  normal  abduction  has  been  found  to  be  about  8°  of 
prism.  While  a  failure  to  overcome  a  prism  of  8°  with  its  base 
toward  the  nose  does  not  prove  that  the  axes  of  the  eyes  are  actually 
balanced  inward,  any  more  than  the  ability  to  overcome  a  prism  of 
a  higher  grade  than  8°  proves  that  they  are  balanced  outward,  the 
abducting  ability  taken  in  relation  with  the  findings  of  the  phorom- 
eter are  of  importance. 

The  restriction  of  the  abducting  ability,  if  exactly  in  proportion 
'with  the  degree  of  esophoria  found,  goes  far  to  exclude  complicating 
conditions  in  the  esophoric  tendency,  while  an  excess  of  abducting 
power  associated  with  esophoria,  as  shown  by  the  phorometer,  would 
go  far  to  indicate  either  an  element  of  hyperphoria  or  an  important 
declination,  or  both.  The  same  may  be  said  of  a  restriction  of  the 
abduction  to  an  extent  considerably  out  of  proportion  to  the  mani- 
fest esophoria.  A  high  degree  of  declination,  mostly  in  one  eye,  not 
unfrequently  gives  rise  to  these  irregularities  of  abduction.1 

Such  facts  indicate  the  importance  of  comparing  the  abducting 
power  and  the  showings  of  the  phorometer.  They  also  indicate  that 
when  one  enters  upon  his  record  the  isolated  fact  that  his  patient  has 
an  abduction,  he  has  stated  nothing  which  is  by  itself  alone  of  prac- 
tical value. 

A  pair  of  eyes,  either  of  which  will  deviate  in  5°  or  more  behind 
a  screen,  may  show  an  abducting  ability  of  12°  or  more,  while  an- 
other pair,  either  of  which  will  deviate  out  5°  or  more  under  similar 
circumstances,  will  overcome  less  than  8°  prism. 

These  facts  do  not  prove  that  there  is  no  value  in  the  test  for 
abduction.  They  show  that  in  order  to  interpret  the  record  of  the 
phorometer  it  is  necessary  to  take  into  account  all  the  actions  of  the 
eye  muscles  as  far  as  it  is  practicable  to  learn  them. 

Such  precaution  is  especially  necessary  if  an  operation  for  the 


1  See  page  245  for  explanation   of  the  swing  from  a   less  to   a  greater 
degree  of  esophoria  or  even  from  esophoria  to  exophoria. 


288  ANOMALIES  OF  MOTOR  MUSCLES. 

correction  of  esophoria  is  contemplated.  A  surgeon  who  determines 
upon  and  performs  a  tenotomy  of  an  internal  rectus,  or  any  opera- 
tion which  might  effect  a  direct  change  in  the  normal  relations  of 
the  visual  lines,  upon  the  evidence  simply  that  a  certain  degree  of 
esophoria  is  found,  might  learn  at  a  somewhat  later  time  that  he  has 
committed  an  error.  These  cases  of  esophoria  with  high  abducting 
ability  are  not  unfrequently  changeable.  The  same  case  which  will 
at  one  time  show  esophoria  of  a  number  of  degrees  may  at  another 
time  show  an  equal  extent  of  exophoria.  The  choice  of  the  eye  for 
most  active  fixation  often  determines  the  direction  in  which  the 
visual  lines  tend.  The  automatic  correction  of  a  positive  declination 
may  induce  exophoria  and  of  a  negative  declination,  esophoria.  Eso- 
phoria then  must  be  studied  in  all  its  relations  in  order  to  lead  to 
appropriate  procedures  for  its  correction. 


SECTION  XXXIX. 

EXOPHORIA. 

The  term  Exophoria  signifies,  according  to  the  definition  at 
page  215,  "a  tending  of  the  visual  lines  outward." 

The  condition,  like  that  of  esophoria,  is  supposed  to  be  ascer- 
tained when  all  the  muscular  tensions  are  at  their  minimum,  and 
especially  when  the  exertions  made  necessary  in  convergence  are,  as- 
nearly  as  possible,  absent. 

As  in  esophoria,  in  order  to  arrive  at  a  knowledge  of  the  con- 
dition the  test  object  must  be  so  far  removed  from  the  eyes  that  a 
full  relaxation  may  be  obtained.  Such  relaxation  demands,  not  that 
the  test  object  should  be  at  an  infinite  distance  when  the  distance 
between  the  eyeballs  is  considered,  for  practically  a  distance  of  not 
less  than  twenty  feet  will  serve  to  place  all  the  ocular  muscles  in  a 
condition  essentially  of  minimum  innervation,  and  will  make  due 
allowance  for  what  is  known  as  the  ''muscular  mesoropter."  At  this 
distance,  then,  if  diplopia  is  induced  by  means  of  a  prism  placed  ex- 
actly vertically  before  one  eye,  or  by  prisms  vertically  placed  before 
each  eye,  the  base  of  one  exactly  up,  of  the  other  exactly  down,  the 
deviation  heteronymously  of  the  two  images  of  an  object  situated  in 
the  same  horizontal  plane  with  the  eyes  is  the  indication  of  exophoria, 
except  so  far  as  the  deviation  is  corrected  by  the  efforts  governed  by 
the  will. 


ESOPHORIA.  289 

As  in  the  case  of  esophoria,  the  phorometer  affords  the  most 
satisfactory  aid  in  making  such  an  examination;  for,  being  placed 
at  a  sufficient  distance  from  the  eyes,  it,  to  a  practical  extent,  neu- 
tralizes the  efforts  to  correct  the  deviation  by  abduction,  permitting 
the  test  to  be  made  under  conditions  more  nearly  approaching  per- 
fect relaxation  of  muscular  tensions  than  any  other  aid,  and  thereby 
avoiding  many  inaccuracies  which  are  unavoidable  by  other  means. 
It  at  the  same  time  reveals  other  complicating  anomalous  tendencies. 
The  number  of  degrees  indicated,  required  for  the  correction  of  the 
heteronymous  deviation  as  shown  by  the  rotating  prisms,  marks  the 
extent  of  exophoria. 

In  exophoria,  as  in  esophoria,  the  habitual  visual  state  is  the 
union  of  the  images  of  the  two  eyes.  When  diplopia  occurs,  the 
deviating  tendency  has  passed  to  actual  deviation  and  is  then  exo- 
tropia.  In  cases  of  exophoria  of  moderate  extent  we  may  discover 
by  the  exclusion  test  that  the  excluded  eye  deviates  outward,  showing 
that  when  the  necessity  for  blending  the  images  no  longer  exists,  the 
normal  direction  of  the  visual  lines  is  in  divergence. 

A  degree  of  exophoria  can  be  maintained  without  passing  to 
exotropia,  which,  in  case  of  a  deviating  tendency  in,  would  result  in 
esotropia,  the  converging  muscles  being  able  to  overcome  a  greater 
deviating  tendency  than  the  diverging  muscles.  Notwithstanding 
this,  an  exophoria  rarely  reaches  10°,  for  the  condition  is  so  gener- 
ally associated  with  hyperphoria,  as  will  be  seen,  that  there  usually 
is  something  more  than  the  simple  outward  deviating  tendency  to 
overcome.  Hence,  after  about  10°,  exophoria  commonly  becomes 
exotropia. 

There  is  usually,  as  shown  by  the  tropometer,  a  power  of  rotation 
out  somewhat  greater  with  exophoria  than  with  orthophoria,  and  the 
inward  rotations  are  slightly  reduced.  Yet,  this  is  not  always  the  case, 
and  in  some  instances  of  exophoria  the  rotation  in  is  even  greater 
than  is  common  in  orthophoria,  while  the  outer  rotation  does  not 
exceed  that  in  the  latter  condition.  Hence,  while  in  certain  cases 
exophoria  might  be  considered  as  the  expression  of  an  actual  diverg- 
ing position  of  the  eyes,  it  cannot  in  all  cases  be  thus  regarded.  The 
percentage  of  exceptions  is  so  large  that  the  rule  cannot  by  any  means 
be  considered  general. 

Another  fact  that  deserves  attention  in  this  connection  is,  that 
while  in  a  certain  proportion  of  cases  the  nearest  point  of  convergence 
is  somewhat  less  near  than  it  is  in  orthophoria,  the  angle  of  conver- 


290  ANOMALIES  OF  MOTOR  MUSCLES. 

gence  in  another  very  large  class  of  cases  of  exophoria  is  greater  than 
is  usual  in  orthophoria. 

Still  another  fact  in  this  connection,  and  one  of  much  impor- 
tance, is  that  exophoria  is  somewhat  rarely  found  in  quite  young 
subjects,  but  occurs  in  greater  frequency  as  adult  age  is  approached. 
When  it  has  once  become  established,  it  is  generally  progressive. 
Esophoria  presents  itself  as  a  noticeable  condition  in  general  at  an 
earlier  age  than  does  exophoria.  From  facts  of  this  kind  it  is  a  log- 
ical conclusion  that  exophoria  is  not  generally,  if  ever,  a  manifesta- 
tion of  a  native  divergence  of  the  visual  lines,  but  is  a  sequence  of 
other  conditions. 

With  exophoria  there  is  commonly  an  increased  abduction  and, 
generally,  in  proportion  to  the  extent  of  exophoria. 

Such  regular  and  proportionate  increase  of  abduction  is  not 
always  present.  It  is  not  rare  to  find  exophoria  with  even  less  abduc- 
tion than  is  usually  found  with  orthophoria.  The  interpupillary 
space  is  not,  in  the  majority  of  cases  of  exophoria,  noticeably  broad- 
ened. When  exophoria  passes  to  exotropia  this  broadening  is,  as  a 
rule,  clearly  seen.  In  most  cases  in  which  the  eyes  appear  to  spread, 
a  condition  of  strabismus  may  be  demonstrated.  On  the  other  hand, 
the  eyes,  even  with  high  degrees  of  exophoria,  are  sometimes  placed 
in  such  unusual  proximity  as  to  suggest  converging  strabismus.  For 
example,  in  the  case  of  a  lad  who  had,  by  the  phorometer,  exophoria 
8°,  by  deviation  in  exclusion  8°,  and  who  had  excessive  abduction,  the" 
pupillary  distance  measured  only  two  inches. 

The  peculiarity  varies  from  the  pressure  of  the  eyes  toward  the 
medial  walls  of  the  orbit  consequent  upon  the  act  of  adjusting  for 
the  declination. 

It  is  important  here  to  repeat  to  some  extent  what  has  been  indi- 
cated more  at  length  in  a  preceding  section  (XXXVII),  that  what  I 
have  called  exophoria  in  accommodation,  which  is  a  condition  anal- 
ogous to  that  called  by  von  Graefe  "insufficiency  of  the  interni,"  does 
not  of  necessity  indicate  a  condition  of  true  exophoria.  Exophoria  in 
accommodation  may  be  associated  with  esophoria,  hyperphoria,  or 
orthophoria.  It  is,  of  itself,  a  condition  without  definite  significance 
in  respect  to  heterophoric  conditions,  but  may  in  some  instances  serve 
as  an  auxiliary  indication  by  which  one  may  be  aided  in  arriving  at 
a  solution  of  an  intricate  problem  in  diagnosis  of  the  true  deviating 
tendencies.  It  would  be  absolutely  inadmissible  to  regard  the  con- 


HYPERPHORIA.  291 

dition  of  "exophoria  in  accommodation"  as  so  much  exophoria.  The 
conditions  are  absolutely  different. 

It  may  not,  in  this  connection,  be  foreign  to  the  subject  to  speak 
of  the  "insufficiency  of  convergence,"  which  has,  in  the  writings  of 
some  continental  authorities,  taken  the  place  of  von  Graefe's  "insuffi- 
ciency of  the  interni." 

If  we  select  indiscriminately  a  number  of  cases  of  simple  exo- 
phoria and  an  equal  number  of  cases  of  hyperphoria,  we  shall  find 
that  the  average  converging  ability  in  the  cases  of  exophoria  is  con- 
siderably greater  than  that  of  the  series  of  cases  of  hyperphoria,  not- 
withstanding the  fact  that  in  some  of  these  cases  there  may  be  eso- 
phoria  in  accommodation.  The  ability  to  converge  is  often  much 
more  considerable  in  cases  where  there  is  actual  divergence  of  the 
optic  axes  than  in  some  cases  in  which  there  is  positive  convergence. 
It  will  thus  be  seen  that  insufficiency  of  convergence  is  by  no  means 
a  sure  indication  that  there  is  any  tendency  on  the  part  of  the  visual 
lines  to  deviate  outward  when  in  a  state  of  repose.  In  other  words, 
insufficiency  of  convergence  is  in  no  way  synonymous  with  exophoria. 
Like  insufficiency  of  the  interni,  it  may  be  a  manifestation  of  the 
effect  of  hyperphoria  or  of  declination. 


SECTION  XL. 

HYPERPHORIA.1 

By  hyperphoria  is  meant  the  condition  of  the  ocular  muscles  in 
which,  with  a  minimum  of  tension,  a  deviation  of  one  visual  line 
above  the  other  would  result.  Habitual  binocular  vision  is  assumed, 
although  we  shall  see  that  it  is  probable  that  in  a  considerable  pro- 
portion of  cases  in  which  hyperphoria  of  more  than  a  single  degree 
exists,  the  tendency  to  diplopia  is  so  great  that  the  subjects  of  the 
affection  often  surrender  to  it — a  fact  confirmed  by  the  marked  am- 
blyopia  often  found  associated  with  this  muscular  condition. 

The  term  hyperphoria  does  not  signify  that  the  visual  line  which  tends 
above  is  too  high  nor  that  the  other  is  too  low.  It  is  absolutely  limited  in 
signification  to  the  fact  stated.  The  whole  visual  plane  of  the  individual  may, 


a  This  chapter  on  "Hyperphoria"  has  been  reproduced,  with  few  changes, 
from  the  first  of  a  series  of  papers  on  the  "Anomalies  of  the  Ocular  Muscles," 
in  the  Archives  of  Ophthalmology,  commencing  in  1887. 


292  ANOMALIES  OF  MOTOR  MUSCLES. 

as  shown  in  Section  XXV  be  too  high  or  too  low  and  in  this  plane  hyperphoria 
may  or  may  not  be  present. 

The  introduction  then  of  a  new  term  to  indicate  that  one  visual  line  is 
lower  than  the  other  is  evidently  superfluous. 

The  first  published  recognitions  of  a  tending  of  one  visual  line  above  the 
other,  less  than  strabismus,  the  condition  now  known  as  hyperphoria,  were  in 
my  Essay  for  the  Royal  Academy  of  Medicine  of  Belgium,  1883,  and  in  my 
classification  of  1880. 

Among  the  varieties  of  heterophoria  none  exerts  a  more  disturb- 
ing or  injurious  influence  than  hyperphoria.  It  is  not  only  a  condi- 
tion giving  rise  in  itself  to  great  fatigue  and  perplexity,  but  it  com- 
plicates and  exaggerates  all  other  faulty  tendencies.  When  we  recall 
the  fact  that  with  a  fair  adducting  power  one  may  overcome  prisms 
of  50°,  with  the  base  to  the  temples,  and  that  with  a  good  abducting 
ability  a  prism  of  7°  or  8°  is  easily  overcome  in  the  opposite  direction, 
it  will  be  apparent  that  muscles  which  do  not  ordinarily  overcome 
more  than  a  prism  of  3°,  as  is  the  case  when  the  prism  is  placed  with 
its  base  up  and  down,  must  be  in  a  condition  of  great  disadvantage 
when  hyperphoria  of  1°  or  2°  exists.  If  we  might  compare  the  rela- 
tive nervous  impulse  demanded  by  the  grade  of  the  prism,  which  can 
be  overcome  in  the  different  directions,  then  a  deviating  tendency  of 
one  visual  line  above  the  other  (hyperphoria)  of  1°  would  be  equal 
to  a  deviating  tendency  outward  (exophoria)  of  more  than  15°.  A 
number  of  important  conditions  are  quite  commonly  found  associated 
with  hyperphoria.  These  conditions  are  local  and  remote.  The  local' 
relate  directly  to  the  function  of  vision,  to  the  adjustments  of  the 
eyes  in  the  performance  of  the  visual  function,  and  to  nervous  dis- 
turbances of  a  functional  or  trophic  nature  in  and  immediately  about 
the  eyes. 

The  remote  conditions  relate  to  a  great  variety  of  disturbances 
of  a  nervous  character  in  parts  more  or  less  removed  from  the  eyes. 

Hyperphoria  of  a  low  grade,  as  determined  by  a  correcting  prism, 
is  very  frequently  attended  by  amblyopia.  It  is  no  unusual  occur- 
rence to  find,  in  a  case  of  hyperphoria  which  may  be  measured  by  a 
prism  of  1°  or  2°,  vision  of  only  20/40  or  even  IGSS>  while  the  refractive 
conditions  arc  not  far  removed  from  emmetropia,  and  the  ophthal- 
moscope reveals  either  no  pathological  state  or  only  a  slight  tendency 
to  the  hypera?mia  about  the  disc  which  is  characteristic  of  irritability 
of  the  eyes  from  muscular  irregularities.  The  relative  number  of 
cases  in  which  such  defective  visual  power  exists  will,  to  one  who  has 


HYPERPHORIA. 


293 


not  well  considered  the  subject,  appear  to  be  out  of  proportion  to  the 
muscular  defect.  The  surprise  will,  however,  give  place  to  conviction 
if  we  bring  clearly  to  mind  the  actual  effects  from  the  standpoint  of 
physiological  optics,  of  a  very  slight  faulty  tendency  in  the  vertical 
direction.  An  actual  deviation  of  a  single  degree  would  result  in  a 
separation  of  images  at  a  distance  of  one-half  meter,  approximately 
of  G.4  millimeters.  A  patient,  then,  with  this  amount  of  deviating 
tendency,  who  would  bring  the  letters  of  the  type  in  which  this  page 
is  printed  even  in  contact,  the  lower  border  of  the  upper  image  touch- 
ing the  upper  border  of  the  lower,  would  be  required  to  exert  a  force 
upon  the  superior  and  inferior  muscles  greater  than  von  Graefe  was 
able  to  exercise.  If,  however,  by  long  practice,  the  muscles  engaged  in 
overcoming  this  fault  acquire  unusual  strength,  as  is  actually  the 
case,  still,  when  the  tension  has  been  continued  for  a  considerable 
time,  or  when  the  general  nervous  tone  is  diminished  from  fatigue 
or  ill  health,  an  almost  irresistible  tendency  to  diplopia  will  occur. 
The  remedy  for  the  confusion  thus  induced  is  a  renewal  of  the  in- 
ordinate muscular  tension  or  the  suppression  of  the  image  of  one  of 
the  eyes.  This  latter  really  takes  place,  and  the  image  suppressed  is 
liable  to  be  that  of  the  eye  in  which  the  greatest  refractive  anomaly  is 
found,  if  a  difference  exists,  or  if  the  eyes  are  equally  well  adapted 
for  clear  vision,  the  suppression  depends  on  other  circumstances 
among  which  the  degree  and  direction  of  declination  are  preeminent. 
In  cases  with  myopia  as  the  ametropic  condition,  the  myopic  eye  may 
be  employed  at  the  near  point,  while  the  more  perfect  eye  is  used  for 
distant  seeing. 

The  extent  to  which  amblyopia  exists  in  connection  with  hyper- 
phoria  is  illustrated  in  the  following  tables.  One  hundred  consecu- 
tive cases  in  which  there  existed  hyperphoria,  and  in  which  no  dis- 

Table  J. 


Refractive  error 

1.00  D  or 

More  than  1.00 
I)  ;  not  exceed- 

More than 
2.50  D  to 

More  than 
4  00  D  to 

Total. 

ing  2.50  D. 

4.00  D. 

o.OOD. 

Emmetropia     . 

45 

Mvopia  .     .     .     . 

9 

19 

7 

I 

42 

Hypermetropia     . 

37 

24 

12 

73 

Astigmatism    . 

28 

7 

5 

40 

74 

50 

24 

7 

200 

294 


ANOMALIES  OF  MOTOR  MUSCLES. 
Table  II. 


Acuteness  of 
vision. 

Refractive  error. 

Total. 

1.00  I)  or  less 

More  than  1.00  D  •  not 
exceeding  2.00  D. 

More  than  2.50  D  ; 
not  exceeding 
5.00  D. 

Best  eye. 

Worst  eye. 

Best  eye. 

Worst  eye. 

Best  eye. 

Worst 
eye. 

fo 
0 
§0 
0 
20 
?0 

38 
22 
6 
1 

21 
15 
8 
2 

7 

o 

3 
2 

'  7 
8 
7 
5 

4 

1 
3 
1 

4 
5 

4 

2 

81 
59 
31 
13 

To 

1 

1 

1 

2 

2 

2 

9 

20 
TOO- 
20_ 

3 
1 

2 

1 

5 
2 

Total 

68 

51 

21 

29 

11 

20 

200 

ease  or  injury  of  the  eyes  was  found,  and  in  which  the  refractive 
errors  were  not  sufficient  to  account  for  any  considerable  defect  of 
vision  when  correcting  glasses  were  used,  are  included  in  the  tables, 
excluding  cases  of  high  grades  of  refractive  errors.  The  highest 
grade  of  astigmatism  not  exceeding  3.00  D,  the  highest  of  hyperopia 
not  exceeding  4.00  D,  and  the  highest  of  myopia  not  exceeding  5.00  D. 

In  the  first  table  the  proportion  of  eyes  affected  with  different 
grades  of  refractive  errors  is  shown ;  in  the  second,  the  acuteness  of 
vision  according  to  the  refractive  condition. 

The  vision  of  the  best  and  worst-seeing  eyes  in  each  grade  is 
given;  but  for  convenience,  in  the  estimate  of  the  comparative  value 
of  the  best  and  worst,  in  all  cases  where  vision  is  equal  in  the  two 
eyes  one  is  reckoned  as  best  and  the  other  worst.  If  anisometropia 
exists  to  the  extent  of  bringing  the  refractive  conditions  of  two  eyes 
in  different  columns,  the  vision  of  one  eye  only  is  placed  in  each 
column. 

From  the  above  tables  we  obtain  the  following  approximate  re- 
sults : — 


AVERAGE  VISION  OF  BEST  EYES. 

Sixty-eight  with  less  than  1.00  D  refractive  error,  1C/20. 
Twenty-one  with  more  than  1.00  D  and  less  than  2.50  refractive 
error,  13/20- 


HYPERPHORIA.  295 

Eleven  with  more  than  2.50  D  and  less  than  5.50  D  refractive 
error,  13/20. 

General  average  of  vision  of  100  best  eyes,  20/30. 

! 

AVERAGE  VISION  OF  WORST  EYES. 

Fifty-one  with  less  than  1.00  D  refractive  error,  14/20. 

Twenty-nine  with  more  than  1.00  D  and  less  than  2.50  D  re- 
fractive error,  12/20. 

Twenty  with  more  than  2.50  D  and  less  than  5.50  D  refractive 
error,  "/20. 

General  average  of  vision  of  100  worst  eyes,  20/50. 

It  will  be  seen  from  the  above  table  that  defective  vision  is  rather 
the  rule  than  the  exception  in  moderate  degrees  of  hyperphoria.  It 
is  a  fact  that  must  have  occurred  to  every  experienced  oculist,  that 
in  anisometropia  a  material  difference  in  the  visual  power  of  the 
two  eyes  is  exceedingly  common.  But  it  is  also  true  that  in  aniso- 
metropia a  difference  in  the  form  of  the  orbits  may  exist,  a  fact  which 
would  tend  to  a  failure  of  equilibrium  in  the  length  or  strength  of 
the  motor  muscles  of  the  eyes.  Experience  confirms  this  reasoning, 
and  I  have  found  that  instances  of  even  approximate  balancing  of 
the  eye  muscles  in  anisometropia  is  rather  exceptional. 

From  the  facts  thus  ascertained  it  becomes  evident  that  ambly- 
opia  is  not  only  very  commonly  associated  with  hyperphoria,  but 
that  it  is  not  uncommonly  a  result  of  that  anomalous  condition. 

A  peculiar  and  interesting  visual  disturbance,  related  to  yet 
differing  from  amblyopia,  is  the  inability  of  the  subject  to  see  small 
objects  clearly,  although  for  larger  objects,  at  the  distance  of  some 
feet,  the  visual  power  is  fair  or  even  good.  Thus,  one  may  be  able 
to  read  Xo.  XXX,  or  even  No.  XX  of  Snellen's  scale,  and  may  have 
no  special  fault  of  accommodation,  yet  when  Xo.  I  is  presented  at 
the  distance  of  one  foot,  the  patient  is  quite  unable  to  read.  Small 
objects  or  characters  are  seen  indistinctly  or  not  at  all.  The  fault 
in  these  cases  appears  to  consist  in  an  inability  completely  to  fuse 
the  images  of  the  two  eyes,  while  the  separation  is  not  sufficiently 
great  to  enable  the  patient  to  easily  suppress  one  of  them.  This  phe- 
nomenon is  illustrated  in  the  confusion  which  appears  when  one 

reads  the  word  here  doubly  printed :  ^S88ffiffl8^8ti8R  If  we  cover 
with  a  card  the  lower  range  of  type,  the  word  is  perfectly  clear.  A 
corresponding  result  may  be  effected  in  a  considerable  degree  of 


296  ANOMALIES  OF  MOTOR  MUSCLES. 

hyperphoria  by  the  mental  suppression  of  the  upper  or  lower  rank 
of  letters.  If,  however,  the  separation  is  less  complete,  as  in  this 
instance :  &4§§§fflffl@d8ti§R  we  are  quite  unable  to  exclude  either  of  the 
confusing  rank?,  as  in  the  former  experiment  with  the  card,  and  the 
difficulty  of  a  mental  exclusion  on  the  part  of  the  subject  of  hyper- 
phoria in  this  latter  case  is  likewise  greater  than  in  one  of  more  com- 
plete displacement.  That  only  a  comparatively  small  proportion  of 
hyperphoric  persons  experience  in  marked  degree  this  inability  to 
see  small  objects  well,  is  probably  to  be  accounted  for  on  the  prin- 
ciple that  in  the  great  majority  of  instances  the  subject  of  hyper- 
phoria is  able  either  to  fuse  the  images  completely,  or  to  displace  them 
to  such  an  extent  as  to  enable  a  mental  exclusion  of  one  image  to 
take  place.1 

The  conditions  of  hyperphoria  relating  to  the  adjustments  of 
the  eyes  through  the  influence  of  the  motor  muscles  are  extremely 
interesting  and  important.  The  disturbing  effect  upon  the  lateral 
equilibrium  is  especially  noticeable,  and  is  a  source  of  great  per- 
plexity to  the  oculist  in  his  examinations  of  the  muscular  relations. 
In  hyperphoria  the  tests  for  lateral  deviations  are  very  often  con- 
tradictory, and  in  a  very  considerable  proportion  of  cases  unsatis- 
factory unless  the  examiner  is  on  his  guard  against  the  anomaly 
under  consideration. 

This  principle  of  apparent  contradiction  is  well  illustrated  in 
such  a  case  as  the  following: — 

I  A  gentleman  was  found  to  have  so  strong  a  tendency  of  the 
visual  axes  to  deviate  inward  that  at  distances  of  twenty  feet  or  more 
much  difficulty  was  experienced  in  maintaining  single  vision.  A 
relaxation  of  the  force  of  the  external  recti  muscles  habitually  re- 
sulted in  homonymous  diplopia.  The  esophoria  as  measured  by 
prisms  was,  however,  not  more  than  4°.  On  the  contrary,  if  the 
gentleman  held  a  pencil  or  his  finger  before  him  at  the  distance  of 
fifteen  or  eighteen  inches  from  the  eyes,  crossed  diplopia  occurred 
from  "insufficiency  of  convergence." 

A  pencil  held  at  fifteen  inches  from  the  eyes  was  doubled  to  an 
extent  that  the  two  images  appeared  about  an  inch  separated.  By 
the  test  of  the  dot  and  line  the  insufficiency  was  only  about  f>°  or  7°. 

This  gentleman  was  found  to  have  hyperphoria  of  5°.     Opera- 


1  While  the  above  paragraph  is  allowed  to  stand  as  published  in  1887,  it  is 
now  evident  that  the  element  of  declination  is  to  be  considered  as  of  im- 
portance in  the  conditions  above  described. 


NATURE  AND  CAUSES  OF  HETEROPHORIA.  297 

ft 

tive  correction  of  the  hyperphoria  resulted  in  permanent  removal  of 
all  annoyance  from  the  double  images  both  near  and  far. 

Instances  of  this  class  are  frequently  encountered  by  one  en- 
gaged in  this  field  of  research.  It  is  evident,  therefore,  that  an 
examination  which  deals  simply  with  "insufficiency  of  convergence," 
exophoria,  or  esophoria  falls  far  short  of  revealing  the  true  condition 
of  the  muscular  balance  of  the  eyes. 

Cases  of  heterophoria  arising  from  high  degrees  of  hyperphoria 
are,  not  unfrequently,  of  alternating  character.  It  may  happen  that 
a  condition  of  esophoria  of  important  degree  at  one  time  may  prove 
to  be  exophoria  of  corresponding  importance  at  a  subsequent  time. 
This  is  not  because  one  set  of  muscles  at  one  time  weak  are  to  be- 
come, at  a  later  period,  too  strong,  while  the  former  strong  ones  are 
to  become  weak.  It  is  because  the  patient  has  for  some  reason  chosen 
to  employ  at  one  time  for  the  most  definite  fixation  one  eye  and  at 
a  later  time  has  selected  the  other  eye  for  this  office.  In  this  way  a 
different  automatic  correction  of  declination  is  effected  at  different 
times,  resulting  in  varying  degrees  of  hyperphoria.  As  a  result  of 
the  different  tensions  induced  by  the  declinations  underlying  the 
hyperphoria,  there  is  the  effect  of  esophoria  at  one  time  and  of  ex- 
ophoria at  another  time.  In  such  cases  the  test  by  abduction  may 
reveal  the  possible  inconsistency  of  the  tendencies. 


SECTION  XLI. 
NATURE  AND  CAUSES  OF  HETEROPHORIA. 

The  tropometer  effectually  disposes  of  the  traditional  "weak- 
ness" of  certain  muscles  as  causes  of  the  different  forms  of  hetero- 
phoria. The  sum  of  the  rotations  temporalward  and  medialward  is, 
in  many  cases  of  esophoria,  greater  than  in  orthophoria,  and  the 
temporal  rotations  in  such  cases  may  exceed  the  outward  rotations 
of  the  ordinary  cases  of  orthophoria.  So  also  the  inward  rotations 
in  exophoria  may  be  excessive.  Clinical  experience  proves  that  at- 
tention properly  directed  in  quite  other  directions  may  correct  the 
tendencies  of  heterophoria  without  direct  interference  with  any  of 
the  muscles  formerly  supposed  to  be  primarily  affected  in  these  anom- 
alous states. 

The  question  of  the  dependence  of  "insufficiency  of  the  interni" 
upon  the  angle  of  the  orbital  axes  was  made  the  subject  of  an  ex- 


298  ANOMALIES  OF  MOTOR  MUSCLES. 

tended  study  by  Dr.  Einil  Emmert,  to  which  reference  has  already 
been  made.1 

Dr.  Emmert's  work  is  illustrated  with  carefully  executed  dia- 
grams of  the  orbital  angles  and  directions  of  the  walls  of  the  orbits 
of  G-i  crania. 

Interesting  and  valuable  as  are  these  researches  they  throw  little 
if  any  light  upon  this  question,  the  relation  of  divergence  of  the  eyes 
and  divergence  of  the  optic  axes. 

The  following  facts  seem  to  bo  established : — 

1.  That  a  certain  excess  of  divergence  of  the  orbital  axes  may, 
in  some  instances,  be  found  and  a  diminished  divergence  in  others, 
is  quite  possible,  although  between  the  clinical  facts  and  such  ana- 
tomical investigations  no  relations  have  thus  far  been  established. 

2.  That  a  condition  of  anophoria  or  of  katophoria  may  influence 
the  directions  of  the  visual  lines  is  evident  when  the  associated  actions 
of  the  various  muscles  are  considered.     It  is  easy  to  explain,  for  exam- 
ple, how  esophoria  may  be  induced  by  the  contending  forces  of  the 
superior  and  inferior  rccti  in  a  case  of  anophoria.     When,  however, 
these  conditions  are  associated  with  important  declinations  the  ele- 
ments of  the  problem  may  be  materially  changed  and  different  results 
may  be  found. 

Bearing  in  mind  the  course  and  the  insertions  of  the  superior 
and  inferior  recti  it  will  be  seen  that  in  a  case  where,  by  reason,  for 
example,  of  a  normal  tendency  for  the  eye  to  be  directed  high,  the 
effort  at  depression  must  induce  a  tension  on  both  the  superior  and 
inferior  recti  simultaneously  which  would  tend  to  swing  the  optic 
axes  toward  the  medial  plane.  (See  Fig.  13,  page  49.) 

3.  That  heterophoria  may  also  be  the  manifestation  of  the  irreg- 
ular insertions  of  the  tendons  into  the  sclera  appears  to  be  indicated 
from  a  study  of  the  results  of  the  investigations  of  Fuchs,  already 
referred  to.2 

It  will  be  seen  from  an  examination  of  the  diagram  which  I 
have  drawn  with  the  view  of  representing  the  insertions  of  the  ten- 
dons as  he  found  them,  that  in  this  variety  of  positions  for  the  inser- 
tions may  be  found  one  cause  for  various  anomalies  in  the  tendencies 
of  the  visual  lines. 

No  estimate  can  be  made  of  the  proportion  of  cases  of  hetero- 


1  See  page  41. 

2  See  page  59. 


NATURE  AND  CAUSES  OF  HETEROPHORIA.  299 

phoria  dependent  on  these  irregularities  of  insertions,  but  it  would 
seem  reasonable  to  assign  to  this  class  of  insertions  at  least  some 
part  in  the  problem  of  heterophoria. 

4.  The  most  conspicuous  demonstrable  cause  known  at  present 
is  found  in  the  directions  of  the  vertical  meridians  of  the  retina. 
That  these  declinations  depend  upon  orbital  peculiarities  and  are 
peculiarities  of  tendon  insertion  is  also  most  probable,  hence,  this 
cause  is  in  a  way  related  to  the  others  already  mentioned. 

The  conditions  of  declination  in  exophoria  and  other  tendencies 
have  been  already  referred  to,  but  in  order  to  bring  the  influence  of 
declinations  on  all  the  forms  of  heterophoria  into  a  general  view  they 
will  be  restated  here. 

Experience  shows  that,  in  general,  the  declinations  of  both  eyes 
are  alike  in  exophoria.  That  is,  if  that  of  one  eye  is  positive,  the 
other  is  also  of  the  same  sign.  The  sum  of  declinations  for  the  two 
eyes  is,  in  exophoria,  usually  considerable.  It  is  rarely  less  than  3° 
to  5°. 

While  the  declination  is  not  always  nearly  equal  for  the  two  eyes 
it  is  found  to  be  so  in  most  cases  of  uncomplicated  exophoria. 

In  order  to  illustrate  the  principle  we  may  now  assume  that  we 
have  to  deal  with  a  case  of  simple  exophoria,  the  normal  visual  plane 
being  not  much  above  or  below  the  standard  plane  for  the  best  ad- 
justments, and  with  a  positive  (-J-)  declination  of  about  equal  degree 
for  each  eye. 

What  is  the  relation  between  the  declinations  and  the  exophoria? 
It  can  be  stated  only  in  general  terms. 

One  of  the  strongest  of  visual  instincts  is  that  relating  to  the 
idea  of  vertically.  If  the  vertical  meridian  of  the  eye  leans,  all 
objects  also  lean.  A  person  looking  directly  forward  with  head  erect, 
to  whom  erect  images  appear  to  lean,  makes  an  automatic  effort  to 
place  the  meridian  of  the  eye  in  an  exactly  erect  position  in  order 
partly  that  the  vertical  meridians  of  the  two  eyes  shall  be  correspond- 
ing meridians.  This,  in  our  case,  demands  an  effort  on  the  part  of 
the  superior  oblique  muscles  out  of  proportion  to  that  of  the  recti. 
As  a  result  the  axis  of  each  eye  is  depressed  and  directed  outward. 
Stress  must  now  be  brought  upon  the  elevating  muscles  to  bring  the 
plane  of  regard  to  the  level  of  the  point  of  regard,  and  upon  the  in- 
ternal recti  to  bring  the  visual  lines  to  unite  at  that  point.  If  diplopia 
is  induced  by  a  prism,  the  automatic  effort  to  maintain  the  erect 
position  of  images  continues,  and  exophoria  is  manifest. 


300  ANOMALIES  OF  MOTOR  MUSCLES. 

This,  of  course,  is  the  proposition  in  its  simplest  form.  That 
no  other  elements  are  introduced  into  the  problem  is  not  to  be 
assumed.  As  a  matter  of  fact,  other  elements  are  usually  involved. 

Hyperphoria  commonly  results  from  less  symmetrical  states  of 
declination.  If,  for  example,  there  is  a  high  degree  of  -|-  declination 
for  the  left  eye  and  a  low  degree  or  no  declination  for  the  right,  we 
have  the  elements  of  right  hyperphoria,  for  in  the  torsional  act  of 
correcting  the  declination  of  the  left  eye,  its  visual  line  may  be  thrown 
below  the  other.  This  does  not  always  happen,  since  other  forces  may 
be  brought  to  bear  to  prevent  hyperphoria. 

The  explanation  of  the  influence  of  declinations  in  inducing 
esophoria  is  much  more  involved  than  that  in  case  of  exophoria  or 
hyperphoria. 

Daily  observation  for  several  years  has  shown  that,  as  a  rule, 
the  declinations  of  exophoria  are  loth  positive,  that  in  hyperphoria 
they  are  unsym  metrical,  and  that  with  esophoria  they  are  conjugate 
but  unequal. 

These  are  the  clinical  facts.  These  efforts  to  explain  them  are, 
as  has  already  been  stated,  only  tentative. 

Taking  for  an  illustrative  case  one  in  which  there  is  pronounced 
positive  declination  for  the  left  eye  and  slight  negative  declination 
for  the  right,  the  resulting  tensions  on  the  adjusting  muscles  which 
will  be  called  into  action  are  these: — 

To  correct  the  positive  declination  of  the  left  eye  the  superior 
oblique  rotates  the  eye  upon  its  axis  and  directs  that  axis  down  and 
out.  The  inferior  oblique,  to  rotate  the  meridian  of  the  right  eye, 
directs  its  axis  out  and  up,  but  to  a  less  extent.  The  superior  rectus 
of  the  left  eye  and  the  inferior  of  the  right  now  come  into  action,  the 
former  with  more  force  than  the  latter,  but  both  acting,  in  propor- 
tion to  the  force  exerted,  to  rotate  the  eyes  inward.  There  remains 
now  the  diverging  effect  upon  the  left  eye  induced  by  the  greater 
action  of  the  superior  oblique,  and  the  internus  of  that  eye  takes  up 
the  burden  of  neutralizing  that  deviation.  Synergically,  the  internus 
of  the  right  eye  also  acts,  and  having  little  to  restrain  it,  it  induces 
an  esophoria. 

In  detail,  the  effects  which  the  various  forms  of  declination  may 
have  upon  the  directions  of  the  visual  axes  where  the  effects  are  un- 
complicated and  manifest  may  be  in  part  summarized  as  follows: — 

Symmetrical  positive  declination  tends  to  cause  a  depression  of 
each  visual  line  with  exophoria. 


NATURE  AND  CAUSES  OF  HETEROPHORIA.  3Q1 

Unilateral  positive  declination  tends  to  hyperphoria,  right,  if 
the  declination  is  left,  and  left,  if  the  declination  is  right.  If  the  eye 
adjusted  for  vertically  is  the  principal  fixing  eye,  there  will  be  exo- 
phoria,  but  if  the  eye  subject  to  the  declination  is  the  principal  fixing 
eye,  there  will  be  esophoria. 

Symmetrical  negative  declination  tends  to  the  presence  of  an 
elevation  of  the  visual  lines.  In  this  case,  as  well  as  in  the  case  of 
positive  declination,  the  actual  direction  of  the  visual  lines  may  be 
contrary  to  that  which  the  declination  would  give,  since  there  may 
be  in  the  case  of  positive  declination  a  marked  condition  of  anophoria 
and  with  negative  declination  as  marked  katophoria,  conditions  too 
pronounced  to  be  overcome  by  the  effects  of  declination. 

With  this  elevation  of  the  visual  axes  there  is  also  a  tendency 
to  exophoria. 

With  unilateral  negative  declination  there  is  the  tendency  to 
hyperphoria,  right,  if  the  declination  is  right,  and  left,  if  the  declina- 
tion is  left.  As  in  the  case  of  positive  unilateral  declination,  exo- 
phoria results  if  the  eye  with  adjustment  for  verticality  is  the  fixation 
eye ;  esophoria,  if  the  eye  with  the  declination  is  in  fixation. 

If  there  is  conjugate  declination  of  equal  extent  there  should 
be  esophoria  with  hyperphoria,  but  the  effects  upon  the  lateral 
tendencies  may  be  neutralized,  or  there  may  even  result  an  exophoria. 

It  is  impracticable  to  enter  here  upon  all  the  shades  of  variation 
which  may  occur  when  the  declination  is  divided  unequally  between 
the  eyes.  The  rules  governing  the  resultant  actions  of  the  muscles 
as  shown  at  page  245,  will  enable  the  investigator  to  determine  ap- 
proximately the  effect  in  individual  cases. 

It  is  to  be  remembered  that  rules  just  stated  apply  only  in  cases 
not  complicated.  In  some  instances  the  effects  of  declination  are 
apparently  in  opposition  to  these  rules,  and  only  the  including  of  the 
complicating -element  will  enable  a  correct  judgment  to  be  formed  as 
to  the  heterophoric  tendency  which  should  be  the  result  in  a  given 
case. 

In  extreme  declination,  strabismus  is  a  frequent  expression  of 
the  surrender  of  the  muscles  to  this  condition.  The  effort  to  main- 
tain verticality  of  the  apparent  positions  of  images,  and  at  the  same 
time  to  regulate  the  collateral  tensions,  is  a  task  which  cannot  be 
maintained  after  the  patient  has  reached  an  age  of  critical  examina- 
tion of  objects. 

That  such  anomalous  adjustments  of  the  eyes  as  are  indicated 


302  ANOMALIES  OF  MOTOR  MUSCLES. 

by  important  grades  of  declination  should  influence  the  pose,  not  only 
of  the  head,  but  of  the  body,  is  no  more  than  might  be  reasonably 
expected.  These  induced  carriages  of  the  head  and  body  are  of  great 
practical  consequence.  In  my  earlier  observations1  I  saw  only  the 
tilting  of  the  head  to  one  side,  but  at  length  I  discovered  that  the 
influence  of  the  adjustments  of  the  eyes  extended  to  the  pose  of  the 
whole  body.  The  subject  has  been  treated  at  some  length  in  the 
section  devoted  to  the  relations  of  the  pose  of  the  body  and  the  nor- 
mal plane  of  vision.  I  have  there  attempted  to  give  only  the  general 
principles.  The  intelligent  observer  will  soon  see  that  the  principles 
extend  to  many  details,  concerning  which  space  has  not  been  sufficient 
to  permit  of  specific  mention. 


SECTION  XLII. 

SUMMARY  OF  PROCEDURE  IN  EXAMINATIONS  FOR  HETEROPHORIA, 
ANOPHORIA,  KATOPHORIA  AND  DECLINATIONS. 

Having  at  such  length  reviewed  the  general  principles  of  ex- 
aminations of  the  muscular  adjustments  of  the  eyes,  it  may  aid  in 
a  practical  understanding  of  the  subject  to  present  a  summary  of  it 
in  a  briefer  manner. 


x  Previous  to  my  own  observations  there  had  been  in  the  literature  of 
science  no  mention  of  these  faulty  positions  of  the  head  or  body  on  account  of 
the  normal  adjustment  of  the  eyes  except  a  remark  by  von  Graefe  that  patients 
with  a  high  degree  of  insufficiency  of  the  interni  sometimes  turn  the  face  to  one 
side  in  order  to  avoid  fixing  the  object  with  the  deviating  eye.  A  few  observa- 
tions had  been  made  in  regard  to  the  pose  of  the  head  in  case  of  paralysis  of 
the  eye  muscles,  but  the  conditions  known  as  heterophoria,  declination,  and 
other  anomalies  of  adjustment  or  of  refraction,  had  received  no  attention  in 
this  relation.  I  first  showed  the  tilting  of  the  head  toward  the  shoulder  in 
cases  of  hyperphoria,  and  I  then  believed  that  the  tilting  was  the  result  of 
hyperphoria  only.  Subsequent  investigation,  when  the  principles  of  declina- 
tion were  understood,  convinced  me  that  the  direction  of  the  vertical  meridians 
is  also  a  most  important  element,  not  only  of  this  particular  pose,  but  of 
others,  such  as  the  elevation  or  depression  of  the  chin  with  or  without  oblique 
deviations.  That  such  carriages  of  the  head  should  also  influence  the  lines  of 
direction  of  tensions  of  the  muscles  of  the  trunk,  and  even  of  the  extremities, 
is  only  the  result  of  mechanical  laws.  As  early  as  1885  I  operated  for  the 
condition  since  known  as  hvperphoria  in  cases  of  chronic  spasm  of  the  muscles 
of  the  neck,  torticollis,  with  partial  success  and  in  many  cases  since  then  simi- 
lar operations  for  the  same  conditions  have  been  done  by  me,  always  with 
encouraging  but  not  with  complete  success,  until  the  relation  of  declination  to 
these  cases  was  recognized.  Since  then  several  extreme  cases  have  yielded 
entirely  to  treatment  of  the  ocular  adjustments. 


SUMMARY  OF  PROCEDURE  IN  EXAMINATIONS.  303 

So  far  as  the  actual  ascertainment  of  the  facts  is  concerned,  it 
may  matter  little  in  what  succession  they  are  obtained.  Yet  in  the 
interest  of  an  orderly  examination,  which  shall  gradually  develop 
the  subject,  there  is  a  natural  sequence  of  the  different  procedures. 

First  of  all,  it  is  best  to  be  informed  of  the  refraction  and  the 
state  of  the  accommodation  as  well  as  the  ophthalmoscopic  appear- 
ances. The  use  of  glasses  may  at  some  subsequent  stage  of  the  ex- 
amination be  absolutely  essential,  and  a  knowledge  of  the  condition 
of  the  interior  of  the  eye  may  be  essential  to  the  examiner  in  order 
to  interpret  what  he  may  find  later. 

The  next  stage  of  the  examination  is  with  the  phorometer. 

In  case,  for  example,  of  the  existence  of  an  important  degree  of 
hyperphoria,  the  findings  by  the  clinoscope  might  be  vitiated  were 
not  means  taken  to  neutralize  in  some  measure  its  effect.  Various 
circumstances  of  this  order  make  it  desirable  to  know  the  results  of 
the  examination  by  the  phorometer  before  proceeding  to  the  other 
stages. 

While  using  the  phorometer  it  should  be  placed  about  five  inches 
in  advance  of  the  eyes  of  the  patient,  and  no  refracting  glasses  should 
be  used  when  the  patient  can  clearly  distinguish  the  test  object  at  the 
proper  distance  without  glasses.  Spherical  glasses  are  prismatic  in 
all  directions;  cylinders  in  some  directions.  All  such  glasses  are 
liable  to  cause  a  leaning  of  the  image  when  the  line  of  regard  is  not 
exactly  through  the  point  of  least  refraction  of  the  glass.  If  the 
reader  will  hold  a  -(-  spherical  glass  of  3  or  4  diopters  sufficiently 
far  in  front  of  his  eye  that  he  will  be  able  to  see  the  upright  casing 
of  a  window  several  feet  distant  partly  through  and  partly  above  and 
below  the  glass,  he  will  see  that  if  the  glass  is  moved  slightly  to  one 
side  and  the  other,  that  part  of  the  casing  seen  through  the  glass  will 
lean,  now  in  one  direction,  then  in  the  other,  while  the  casing  not  seen 
through  the  glass  will  of  course  remain  upright.  These  leanings  of 
the  image  may  in  some  degree  neutralize  an  existing  declination  of 
the  eye  and  thereby  modify  the  heterophoria  test,  or  it  may  induce 
an  effort  corresponding  to  that  for  correcting  declination,  and  thus 
also  induce  a  heterophoric  condition.  There  are  several  objections  to 
the  use  of  lenses  with  the  phorometer,  and  there  are  no  reasons,  except 
inability  to  see,  for  their  use. 

The  test  object,  a  lighted  candle,  should  be  removed  twenty  feet 
from  the  patient. 

A  record  of  the  phorometric  conditions  having  been  made,  the 


304  ANOMALIES  OF  MOTOR  MUSCLES. 

abduction  and  sursumduction  may  be  tested  at  the  same  distance.  The 
simplest  and  easiest  and,  indeed,  the  most  effective  way  of  making 
these  tests  is  by  the  help  of  prisms  taken  from  the  trial  case.  Nu- 
merous devices,  modifications  of  the  Cretes  prism,  have  been  sug- 
gested. They  are  clumsy  and  impracticable. 

For  abduction,  take  a  prism,  for  example,  of  5°  from  the  box. 
Place  it  with  its  base  toward  the  nose  close  to  one  eye  of  the  patient, 
and  ask  him  to  unite  the  images,  if  two  result.  If  this  can  be  done, 
proceed  to  the  next  grade  or  pass  over  one  or  two  grades  and  try 
again.  In  a  very  few  trials  the  limit  will  be  reached.  On  the  other 
hand,  if  the  5°  prism  cannot  be  overcome,  a  lesser  grade  is  tried, 
and,  if  necessar}-,  other  lesser  ones,  until  a  union  of  images  can  be 
found.  The  strongest  prism  that  can  be  overcome  is  the  measure  of 
abduction.  If  there  is  an  actual  convergence  it  may  require  a  prism 
with  the  base  out  to  enable  the  patient  to  unite.  Then  there  is 
homonymous  diplopia  of  the  degree  of  the  weakest  prism  that  will 
unite  the  images.  Prisms  of  much  less  grade  are  usually  required 
for  sursumduction.  A  prism  of  1°,  2°,  or  3°  is  usually  sufficient. 

Place  the  prism  with  its  base  down  before  one  eye.  If  this  can 
be  overcome,  present  a  stronger  until  with  no  stronger  will  the  images 
unite.  In  most  cases  a  prism  of  not  more  than  3°  may  be  overcome. 
In  myopic  cases  with  high  declinations,  prisms  of  9°  or  10°  may  be 
overcome.  After  determining  the  sursumduction  in  one  direction, 
the  examination  in  the  other  should  be  deferred  for  some  minutes 
until  the  effect  of  the  first  efforts  has  passed  off.  Then  the  prism 
may  be  placed  before  the  second  eye  with  its  base  in  the  same  direc- 
tion as  before,  or  before  the  same  eye  with  its  base  reversed.  The 
result  will  be  the  same  in  either  case.  These  tests  being  completed 
satisfactorily,  the  tropometer  is  brought  into  use.  A  knowledge  of 
the  rotations  up  and  down  is  of  more  importance  than  that  of  the 
lateral  rotations,  since  the  latter  are  very  frequently  modified  by  the 
former. 

The  patient  seizes  the  wooden  tooth-rest  firmly  by  the  teeth  and 
presses  the  forehead  against  the  arch  of  the  head-rest.  Then  the 
examiner  sees  that  the  head  is  so  adjusted  that  the  upper  button  of 
the  guards  presses  at  the  glabella  and  the  lower  button  presses  equally 
at  the  depression  of  the  jaw  below  the  nasal  spine.  The  eye  is  directed 
to  the  objective  point  on  the  instrument  and  the  surgeon  adjusts  the 
scale  to  the  border  of  the  cornea.  After  careful  attention  to  these 
details,  the  examiner,  holding  the  patient's  head  with  his  hand  to 


SUMMARY  OF  PROCEDURE   IN  EXAMINATIONS.  305 

prevent  or  detect  any  movements,  directs  the  patient  to  direct  the  eyes 
as  far  up  as  possible.  The  effort  is  repeated  until  the  patient  is  able 
to  bring  all  the  force  at  his  command  to  the  action.  The  highest 
point  of  rotation  as  shown  by  the  scale  is  noted,  and  the  upward  rota- 
tion of  the  opposite  eye  is  determined  in  the  same  manner. 

The  downward  rotations  are  also  noted,  and  then,  if  the  exam- 
iner desires,  the  scale  is  turned  and  the  lateral  movements  are  exam- 
ined. 

The  final  stage  is  with  the  clinoscope.  The  tubes  are  brought 
to  a  level  with  the  eyes  and  the  instrument  is  brought  to  an  exact 
level  as  shown  by  the  upper  spirit  level.  The  finer  sight-holes  are 
adjusted  for  the  interpupillary  distance  and  the  tubes  are  adjusted 
in  parallelism.  The  patient,  looking  through  the  sight-holes,  must 
see  both  test  objects  at  the  same  time,  and  continue  to  do  so  during 
the  whole  examination.  The  examiner  brings  one,  then  the  other 
test  line  to  an  exact  vertical  position  as  seen  by  the  patient.  No  sug- 
gestion should  be  made  which  will  aid  the  patient  as  to  the  direction. 
No  refracting  glass  except  such  as  is  positively  demanded  to  enable 
the  patient  to  see  the  test  lines  or  a  prism  for  correcting  hyperphoria 
should  be  used,  and,  in  order  to  avoid  false  leanings  induced  by  a 
glass,  it  should  be  placed  in  the  clip  when  the  line  of  regard  will 
not  pass  through  it  obliquely.  The  pointer  should  be  moved  back- 
ward and  forward  until  the  examiner  is  sure  that  the  patient  is  exact 
in  his  impression  as  to  its  verticality.  The  second  pointer  is  then 

FOBM  OF  BLANK  FOB  DAILY  MEMORANDUM,  SIZE  3}  x  5  INCHES. 


Mr -- 

189 

Hyperphoria,   B., L., 

Exophoria Exophoria 

Abduct Adduct 

Sursumduct.  B.,  //., 

Dev.  in  ExcJus. Conv.  at 

(B. 
Botation,  •{ 

(L. 

(B. 

v=\ 
(L. 

Declination,  B., L., 

Operat.,  Prescrip.,  Clinical  Notes,  etc. 


306  ANOMALIES  OF  MOTOR  MUSCLES. 

adjusted  with  equal  care.  Then  the  position  of  the  first  is  revised 
and  time  enough  is  given  to  permit  the  eyes  to  relax  from  the  habitual 
adjustments  which  are  required  in  their  ordinary  use. 

By  these  various  processes  the  examiner  has  put  himself  in  pos- 
session of  a  considerable  number  of  important  and  correlative  facts 
upon  which  he  is  able  to  base  his  conclusion  in  regard  to'  the  actual 
state  of  the  muscular  adjustments.  All  are  necessary  elements  in  the 
problem,  and  no  examination  can  be  said  to  afford  the  means  for  a 
correct  determination  of  the  adjustment  relations  which  does  not  in- 
clude the  refraction,  the  results  by  the  phorometer,  those  by  the 
tropometer,  and  those  by  the  clinoscope.  In  order  to  be  able  to  see 
the  results  at  a  glance  as  well  as  to  have  a  temporary  record  which 
may  be  transferred  to  the  case  book  after  the  work  of  the  day  is  over,  I 
have  for  many  years  used  a  small  slip  containing  a  form,  filling  it 
for  each  case  as  examinations  are  made,  destroying  them  when  the 
results  are  entered  in  the  case  book. 


SECTION  XLIII. 
CLINICAL  FEATURES   OF  THE  NON-STRABISMIC   ANOMALIES   OF 

THE  OCULAR  MUSCLES. 
HETEROPHORIA. 

While  mindful  of  the  fact  that  a  very  important  proportion  of 
cases  of  heterophoria  have  their  origin  in  declinations  or  in  the  un- 
favorable location  of  the  normal  plane  of  vision,  and  that  hence  the 
general  symptoms  of  heterophoria  may  in  large  measure  represent 
conditions  arising  from  the  original  causes,  still  there  are  such  special 
clinical  features  associated  with  the  different  forms  of  heterophoria 
that  it  is  desirable  to  examine  these  features  in  connection  with  the 
more  immediate  muscular  anomalies. 

In  respect  to  the  clinical  importance  of  esophoria,1  which  occurs 
in  the  proportion  of  more  than  three  to  one  of  exophoria,  it  plays  a 
much  more  important  role  than  the  latter  as  a  predisposing  cause  to 
a  variety  of  neuroses ;  and,  as  the  immediate  cause  of  asthenopia  and 
kindred  affections  about  the  eyes,  it  is  an  element  of  great  disturb- 


1  This  section  is  largely  reproduced  from  my  "Second  Paper"  in  the  series 
in  Archives  of  Ophthalmology,  1888,  page  177  et  seq.,  with  such  modifications 
as  more  recent  observations  have  rendered  necessary. 


CLINICAL  FEATURES.  307 

ance.  It  is  true  that  in  individual  cases  of  exophoria  the  strain  in 
adjusting  the  eyes,  especially  in  reading  and  other  close  work,  may 
be  more  immediately  expressed  in  the  orbit  in  the  form  of  localized 
pain  of  the  muscles,  than  in  an  average  case  of  esophoria  of  equal 
extent.  The  reactions  of  esophoria  are  likely  to  be  more  distant. 
Thus,  a  patient  affected  with  exophoria  may,  after  an  hour  spent  in 
reading,  suffer  from  pain  in  and  immediately  about  the  orbit.  On  the 
other  hand,  a  patient  affected  with  esophoria,  after  attending  church 
or  the  opera  or  after  visiting  a  picture  gallery,  where  the  eyes  have 
been  directed  during  a  considerable  time  at  a  distant  point,  and  in 
such  a  position  as  to  make  it  necessary  to  hold  the  visual  lines  in 
parallelism,  is  quite  likely  to  experience  a  universal  malaise,  with 
pain  at  the  back  of  the  head  and  in  the  upper  part  of  the  neck,  and 
possibly,  if  the  patient  is  not  strong,  a  sense  of  illness  all  the  follow- 
ing day. 

Eeviewing  a  large  experience  in  comparing  these  two  conditions, 
I  find  that  the  general  or  distant  reactions  from  esophoria  are  far 
more  frequent  and  significant  than  those  of  exophoria,  and  that  the 
local  pains,  while  possibly  absent  in  a  greater  proportion  of  cases, 
are  still  of  great  prevalence  and  of  a  more  persistent  character  where 
existing. 

The  grade  of  the  deviating  tendency  does  not  always  mark  the 
extent  of  irritation  resulting  from  it.  Indeed,  it  often  happens  that 
less  serious  reactions  result  when  the  anomalous  conditions  are  ex- 
treme than  when  they  are  moderate.  Thus,  in  a  case  of  esophoria  or 
exophoria  of  2°  or  3°,  the  defect  is  sonletimes  a  source  of  greater 
irritation  than  one  on  the  verge  of  strabismus,  of  8°  or  9°,  because, 
in  the  first  instance,  binocular  vision  is  constant,  or  nearly  so,  al- 
though effected  by  a  strenuous  effort.  In  the  second  case  the  image  of 
one  eye  is  often  suppressed,  for  very  short  or  longer  periods  of  time, 
and  one  of  the  eyes  is  permitted  to  drift  away  from  the  physiological 
companionship  of  its  fellow,  thus  affording  a  rest  of  one  kind  at  the 
expense  of  another  sort  of  nervous  perplexity. 

It  is  not  to  be  supposed  that  because  esophoria  is  more  often 
than  exophoria  the  predisposing  cause  of  distant  disturbances,  it  is 
therefore  not  a  notable  cause  of  asthenopia.  Of  a  large  class  of  cases 
which  go  from  one  oculist  to  another  in  the  hope  of  relief  from  some 
new  treatment,  and  submit  to  an  almost  endless  change  of  spectacles 
with  little  if  any  advantage,  a  very  considerable  number  are  victims 
of  very  slight  grades  of  esophoria.  They  gain  no  relief  until  this  too 


308  ANOMALIES  OF  MOTOR  MUSCLES. 

much  neglected  anomaly  receives  due  attention,  when  their  asthen- 
opic  symptoms  disappear.  These  very  moderate  cases  of  esophoria 
may  represent  important  declinations,  and  it  is  these  latter  conditions 
which  induce  the  nervous  perplexity  rather  than  the  slight  resulting 
esophoria. 

To  the  ordinary  phenomena  of  asthenopia  may  be  added  the 
following  symptoms  which  are  prominent  among  the  local  indications 
of  esophoria. 

In  a  certain  proportion  of  cases,  especially  those  in  which  eso- 
phoria approaches  the  extreme  limits  to  which  binocular  vision  can 
be  maintained,  the  accommodation  is  feeble  and  the  pupil  is  slug- 
gish and  dilated.  It  is  quite  certain  that  in  such  cases  there  is  a 
failure  to  accommodate  quickly,  for  some  other  reason  than  the  sup- 
pression of  the  habitual  relation  between  the  convergence  and  the 
accommodation,  since  even  after  entirely  successful  operations  for 
the  relief  of  esophoria,  the  accommodation  remains  enfeebled  and  the 
pupil  sluggish  and  expanded,  with  a  continuance  of  the  symptoms 
of  asthenopia  and  headache.  Attention  to  the  declination  which  may 
induce  the  esophoria  usually  restores  the  accommodation  to  full  vigor, 
with  quick  reactions  of  the  pupil. 

In  esophoria,  especially  when  combined  with  hyperphoria,  one 
of  the  very  unpleasant  symptoms  not  unfrequently  met  with  is  the 
annoyance  experienced  by  the  patient  in  constantly  seeing  the  nose. 
This  may  appear  a  trivial  symptom,  yet  it  is  described  by  those  sub- 
ject to  it  as  a  most  vexatious  phenomenon.  Many  patients  declare 
that  they  can  bear  the  pain  of  the  head  and  back  resulting  from  the 
muscular  conditions  better  than  they  can  endure  the  never-ceasing 
annoyance  of  seeing  the  nose. 

In  similar  conditions  patients  not  unfrequently  complain  of 
seeing  a  black  spot  in  the  center  of  the  field  of  vision.  Thus,  while 
reading,  the  black  spot  will  appear  at  or  near  the  part  of  the  page 
at  which  the  reader  is  looking,  causing  annoyance  and  confusion. 
There  may  be  different  explanations  for  the  appearance  of  this, 
scotoma.  In  some  instances  it  is  probable  that  the  dark  spot  repre- 
sents the  shadow  of  a  vessel  of  the  retina,  while  in  more  rare  cases 
it  is  possible  that  the  scotoma  is  caused  by  the  intrusion  of  the  blind 
spot  into  the  line  of  regard. 

The  effect  of  esophoria  on  vision,  while  in  the  lesser  degrees  it 
is  not  so  pronounced  as  that  which  has  been  shown  to  result  from 


CLINICAL  FEATURES.  309 

slight  grades  of  hyperphoria,  is,  in  moderately  high  degrees,  of  a 
most  unequivocal  character. 

Amblyopia  has  been  shown  (Section  XL)  to  be  rather  the  rule 
than  the  exception  in  cases  of  hyperphoria.  In  esophoria,  amblyopia 
of  at  least  one  eye  is  quite  common  when  the  deviating  tendency 
exceeds  3°. 

In  one  of  my  early  contributions  to  the  subject  of  esophoria1  I 
have  shown  the  relation  between  uncomplicated  cases  of  esophoria  and 
amblyopia.  From  a  table  of  100  such  cases  it  appears  that  there  is 
an  average  loss  of  visual  power  in  cases  of  esophoria  of  more  than 
3°  of  about  one-third  in  one  or  other  eye. 

It  is  only  reasonable  to  suppose  that  a  condition  which  must  of 
necessity  act  as  a  constant  cause  of  nervous  perplexity  and  irritation, 
should  result  in  inducing  a  state  of  hyperasmia  or  of  altered  nutrition 
of  the  parts  supplied  to  a  certain  extent  by  branches  of  the  same 
nerves  which  supply  the  imperfectly  balanced  muscles.  It  could 
scarcely  happen  that  an  irritative  cause  so  prolonged  in  its  existence 
and  so  efficient  in  inducing  functional  disturbances  should  fail  to  be 
a  frequent  cause  of  such  perverted  nervous  influences  upon  the  eyes 
themselves  or  their  immediate  surroundings  as  to  promote  patho- 
logical changes  of  diverse  forms. 

Hence,  for  instance,  it  is  not  a  surprising  fact  that  one  who, 
during  a  lifetime,  has  contended  with  the  irritating  influences  of 
heterophoria,  should  at  length  find  that  the  nutrition  of  the  crystal- 
line lens  has  suffered  degenerative  changes,  or  that  even  the  tunics  of 
the  eye  should  be  affected  unfavorably. 

This  view  of  the  possible  or  probable  origin  of  many  affections 
of  the  eye  is  not  one  to  be  regarded  with  neglect  or  disdain  or  treated 
as  the  outgrowth  of  extreme  views.  Diseases  do  not  occur  spontane- 
ously. They  are  the  result  of  laws,  and  it  is  idle  to  speak  of  cataract 
or  corneal  ulcer  or  of  various  other  affections  simply  as  accidental  or 
Providential  visitations;  and  a  fallacy  to  talk  of  "constitutional 
causes"  when  we  simply  mean  that  we  do  not  know.  A  known  cause 
which  may  induce  perverted  nerves  is  of  more  practical  consequence 
than  a  volume  of  profound  ambiguity. 

Many  years  ago  I  called  attention  to  the  influence  of  refractive 
anomalies  as  predisposing  causes  of  corneal  ulcers2  and  to  other 


1  "Anomalies   of  the  Ocular  Muscles,   Second  Paper,"   Archives    of   Oph- 
thalmology, 1888. 

2  "Transactions,  International  Congress,"  Philadelphia,  1876. 


310  ANOMALIES  OF  MOTOR  MUSCLES. 

chronic  diseases  of  the  eyes  and  lids,  and  I  have  since  had  the  satis- 
faction of  noticing  that  several  close  observers  have  arrived  at  similar 
conclusions.  There  is  no  reasonable  doubt  that  refractive  and  mus- 
cular lesions  are  very  largely  effective  in  the  causation  of  various  eye 
affections,  both  internal  and  external.  True,  there  are  certain  well- 
known  general  physical  taints  and  impairments  which  are  manifested 
as  local  affections;  but  even  in  the  presence  of  these  sources  of  evil 
we  may  learn  that  the  localizing  of  the  virulence  is  favored  by  a 
damaged  or  enfeebled  state  of  the  nerves  supplying  the  affected  part. 

Hence  in  many  chronic  and  obdurate  affections  of  the  eye  we 
may  look  upon  the  conditions  of  anomalies  of  refraction  and  of  the 
adjustments  as  possible  or  probable  sources  of  mischief. 

Should  a  case  of  incipient  idiopathic  cataract  present  itself,  and 
should  it  be  found  associated  with  pronounced  anomalies  of  the  eye 
muscles,  and  should  these  anomalies  be  properly  treated  and  corrected, 
would  the  cataract  stop  ?  Perhaps  not.  But  in  many  cases  within  my 
experience  it  has  stopped.  It  would  be  doing  an  intelligent  act  to 
relieve  the  patient  from  a  source  of  irritation  which  might  affect  the 
nutrition  of  the  lens  unfavorably.  The  arrest  of  the  complaint  might 
not  follow,  but  the  surgeon  has  made  no  mistake  if  he  performs  his 
work  well,  and  he  has  a  reasonable  expectation  that  the  pathological 
process  may  be  arrested. 

I  have  reproduced  this  whole  section  as  it  was  published  in  1888,  with 
twTo  or  three  verbal  corrections  in  order  to  present  these  views  exactly  as  they 
were  then  written.  Long  before  this  I  had  recognized  this  class  of  causes  as 
extremely  influential  in  the  aetiology  of  many  forms  of  eye  diseases.  In  the 
paragraph  above,  more  particularly,  reference  is  made  to  cataract,  not  because 
it  was  then  supposed  to  be  more  than  many  other  forms  of  eye  affections,  a 
manifestation  of  the  evil  influences  of  the  class  of  anomalies  under  discussion, 
but  as  a  common  and  representative  form  of  nutritive  disturbances.  That 
diseases  of  the  retina,  of  the  choroid,  of  the  cornea,  and  of  the  optic  nerves,  as 
well  as  other  structures  of  the  eyes,  not  only  frequently  but  commonly  have 
one  or  other  of  the  anomalous  states  of  the  eye  muscles  as  an  important  and 
sometimes  almost  exclusive  factor  in  their  aetiology,  I  did  not  then  doubt  nor 
do  I  now,  after  the  lapse  of  many  years.  This  book  is  not  intended  to  enter 
upon  the  different  forms  of  diseases  of  the  eyes,  and  it  is  not  necessary  to 
specify  how  or  when  muscular  anomalies  may  induce  special  forms  of  eye 
troubles.  The  principle  that  they  are  setiological  factors  is  all  that  nee;l  be 
here  stated. 

Blepharitis,  with  its  redness  of  the  eye1  ids  and  chronic  red- 
ness of  the  ocular  conjunctiva,  is  a  frequent  result  of  esophoria.  As 
to  more  distant  effects  a  large  class  of  people  who  from  year  to  year 


CLINICAL  FEATURES.  311 

are  supposed  to  suffer  from  "malaria,"  "biliousness,"  "nervous  pros- 
tration," "dyspepsia,"  "constipation,"  and  similar  neurasthenic  con- 
ditions are  simply  paying  the  penalty  of  uncorrected  heterophoria. 
The  effects  of  one  or  other  forms  of  heterophoria  are  frequently  seen 
in  their  influence  upon  the  physical  functions.  Chronic  constipation, 
dysuria,  and  dysmenorrhoea  are  not  infrequent  results  of  the  hetero- 
phoria. 

The  reactions  from  exophoria  are  in  many  respects  similar  to 
those  of  esophoria,  though,  as  above  stated,  those  of  exophoria  are 
more  frequently  of  a  local  character. 

Still,  pains  in  distant  parts,  nausea,  dizziness,  and  other  neu- 
roses are  frequent  responses  to  the  difficulties  of  adjustments  arising 
from  exophoria.  In  general,  the  remarks  applied  to  esophoria  may 
apply  also  to  exophoria.  The  head  is  frequently  thrown  backward  as 
a  habitual  pose  with  exophoria,  a  pose  due  to  the  double  -{-  declina- 
tion, resulting  in  habitual  pain  at  the  back  of  the  head  and  neck. 

The  more  remote  results  of  hyperphoria  are  similar  to  other 
anomalies  of  the  ocular  muscles,  but  with  certain  special  character- 
istics. Neuralgia,  neurasthenia,  insomnia,  chorea,  and  epilepsy  are 
among  the  manifestations  of  hyperphoria,  as  they  are,  indeed,  of  the 
other  forms  of  heterophoria,  but  to  a  greater  extent  than  the  other 
forms  is  this  one  associated  with  chronic  vertigo  and  pure  epilepsy. 
The  nervous  disturbance  arising  from  this  cause  is  more  perplexing, 
both  from  the  difficulty  of  overcoming  it  by  ordinary  effort  and  from 
the  complications  arising  from  it  in  respect  to  the  converging  and 
diverging  efforts,  than  moderate  grades  of  deviating  tendencies  in  the 
lateral  direction.  Beyond  all,  the  markedly  unsymmetrical  declina- 
tions which  are  associated  with  and  are  doubtless  the  cause  of  most 
cases  of  hyperphoria  are  conducive  to  such  conditions  as  vertigo  and 
epilepsy  as  well  as  to  a  great  variety  of  nervous  irregularities. 

The  carriage  of  the  head  to  one  side  which  is  a  pose  character- 
istic of  hyperphoria,  and  which  is  also  one  of  the  effects  of  conjugate 
or  of  quite  unequal  declination,  is  often  a  source  of  much  discom- 
fort by  reason  of  the  contraction  of  one  set  of  muscles  and  the  exten- 
sion of  another.  It  is  not  uncommon  for  persons  with  hyperphoria 
to  experience  much  pain  in  the  back  of  one  side  of  the  neck,  pain 
which  is  habitual  during  many  years,  and  chronic  spasmodic  affec- 
tions of  the  neck  muscles  sometimes  result.  Such  cases  are  often 
relieved  fully  and  at  once  by  an  appropriate  operation  for  the  cor- 
rection of  the  ocular  muscle  anomaly. 


312  ANOMALIES  OF  MOTOR  MUSCLES. 

In  concluding  these  pages  devoted  to  pointing  out  some  of  the 
clinical  features  of  the  different  forms  of  heterophoria,  I  must  revert 
to  Section  XXXIII,  where  it  is  stated  that  "as  a  matter  of  fact  hetero- 
phoria may  lie  regarded  as,  in  general,  a  resultant  of  declinations  and 
of  adjustments  of  the  eyes  above  or  below  a  certain*  plane  relative  to 
the  cranium."  The  different  clinical  features  of  the  forms  of  hetero- 
phoria are  in  fact  the  expression  of  the  different  combinations  of 
declinations  and  adjustments  for  an  unfavorable  plane.  Thus,  the 
head  is  often  carried  high  in  exophoria  although  the  rotations  may 
be  high,  because  of  the  existence  of  positive  declination  of  both  eyes. 
So  also  pain  in  one  or  both  sides  of  the  neck  may  arise  in  esophoria 
because,  resulting  from  a  high  degree  of  conjugate  declinations,  the 
head  is  carried  far  to  one  side.  Many  illustrations  might  be  adduced 
to  show  the  principle,  but  it  is  needless  to  point  out  in  detail  all  the 
relations  of  this  kind. 

"What  is  most  important  is  to  remember  that,  while  for  conven- 
ience, with  the  different  forms  of  heterophoria  various  clinical  feat- 
ures have  been  associated,  it  is  to  the  underlying  conditions  of  hetero- 
phoria that  we  must  look  for  the  explanation  of  these  clinical  features, 
and  that  in  the  practical  management  we  are  to  look  to  these  inducing 
causes  of  heterophoria  rather  than  directly  to  the  heterophoric  mani- 
festations themselves  for  the  most  effective  and  enduring  relief. 


ANOPHORIA,    KATOPHORIA,    AXD    DECLINATION". 

Of  the  more  local  affections  to  which  anophoria  or  declination 
may  give  rise,  hyperremia  of  the  palpebral  conjunctiva  is  perhaps  the 
most  frequent.  I  mention  anophoria  and  declination  together,  since 
they  may  give  rise  to  similar  phenomena.  Thus,  in  anophoria  the 
axes  of  the  eyes  being  inclined  to  rise  above  the  most  favorable  plane, 
the  eyelids  aid  the  depressor  muscles  by  bringing  pressure  upon  the 
upper  surface  of  the  eyeball.  Very  nearly  the  same  thing  happens 
with  certain  forms  of  declination  in  which  the  lids  clasp  the  eyes  to 
aid  in  maintaining  satisfactory  adjustments. 

In  both  cases  the  pressure  upon  the  eyeballs  may  and  often  does 
give  rise  to  hyperffimia  of  the  lids,  which  may  be  relieved  by  treat- 
ment, but  which  returns  soon  after  treatment  is  discontinued. 

With  anophoria  of  high  degree  associated  with  important  de- 
clinations, there  exist  the  conditions  favorable  to  the  deve^pment  of 


ANOPHORIA,  KATOPHORIA,  AND  DECLINATION.  313 

trachoma,  and  I  have  shown1  that  it  is  in  connection  with  these  con- 
ditions that  trachoma  occurs.  I  am  able  to  add  that  I  have  seen  most 
luxuriant  follicular  hypertrophy  of  the  conjunctiva  of  the  lids  melt 
away  with  surprising  rapidity  when  the  tensions  for  anophoria  and 
declination  have  been  relieved. 

I  have,  in  illustration  of  this  proposition,  used  in  one  or  more 
of  my  contributions  to  this  subject  mentioned,  the  following  inter- 
esting facts: — 

A  few  years  since  a  distinguished  oculist  of  one  of  our  Southern 
cities  announced  that  trachoma,  that  form  of  eye  trouble  commonly 
known  as  granular  lids,  and  which  is  one  of  the  prolific  sources  of 
blindness,  is  unknown  among  pure  negroes.  The  discussion  of  this 
proposition,  after  occupying  the  attention  of  oculists  for  some  time, 
was  at  length  taken  up  in  a  different  way  by  a  distinguished  colleague 
in  Constantinople. 

This  gentleman  wrote  to  oculists  in  all  parts  of  the  world  asking 
for  the  results  of  their  observations  in  their  own  countries  in  regard 
to  all  classes  of  people.  He  at  length  published  a  symposium  of  the 
answers  showing  the  prevalence  of  trachoma  in  different  countries  and 
among  the  different  classes  of  people.  As  given  in  this  contribution 
there  seemed  to  be  a  confused  accumulation  of  facts  which  had,  on  the 
whole,  apparently  little  meaning.  Peoples  of  contiguous  countries,  of 
the  same  color  and  not  very  different  in  habits  of  life,  were  reported 
as  differing  widely  in  respect  to  the  prevalence  of  the  affection.  Xo 
reasons  were  assigned  and  none  seemed  to  be  suggested  by  the  varying 
facts.  An  analysis  which  I  made  of  this  report  showed  that  among 
peoples  with  the  'medium'  or  tall  heads,  like  the  Irish  and  the  Italians, 
trachoma  is  rife;,  while  among  peoples  with  the  broad  head,  like  the 
Bavarians,  or  with  the  long  head,  like  the  negroes  whose  ancestors 
were  from  the  West  or  Guinea  coast  of  Africa,  trachoma  did  not  pre- 
vail; but  it  is  interesting  to  note  that  descendants  of  the  negroes  of 
the  northern  part  of  Africa,  where  the  heads  of  the  natives  are  often 
tall,  are  subject  to  trachoma  equally  with  the  whites  among  whom 
they  live.  I  have  in  another  connection  discussed  this  question  at 
more  length. 

A  glance  at  Fig.  109  will  show  that  the  negro,  as  he  is  known 
in  our  Southern  States,  not  onlv  throws  the  head  backward  in  the 


1  Paper  read  at  British  Medical  Association,  August,  1897.      Published  in 
Ophthalmic  Review,  September,  1897, 


314 


ANOMALIES  OF  MOTOR  MUSCLES. 


manner  characteristic  of  the  long  head,  the  strong  facial  angle  and 
the  depressed  visual  plane,  but  that  the  eyebrows  are  characteristically 
elevated.  This  drawing  up  of  the  brow  is  accompanied  with  a  draw- 
ing upon  the  lids,  and  hence  no  pressure  is  brought  upon  the  surface 
of  the  eyes  by  the  upper  lids.  In  the  case  of  the  tall  head  with  the 
high  plane  of  vision  the  brows  are  strongly  compressed  and  the  lids 
bind  upon  the  eyeball,  and  thus  in  the  midst  of  dust  and  filth  or  even 
in  good  sanitary  surroundings  disease  of  the  lids  may  be  promoted. 
The  carriage  of  the  head  too  far  in  advance  or  too  far  backward 
is  directly  governed  by  the  state  of  the  muscular  adjustment  of  the 
eyes,  and  from  or.e  or  other  of  these  habitual  carriages  may  arise  a 


Fig.  109.— The  Long  Head  with  Prognathous  Face.     Facial  angle  +  15C 


variety  of  unpleasant  or  injurious  effects.  In  another  section  the 
tendency  to  restrict  the  respiration  by  the  carriage  of  the  head  in 
advance  has  been  already  dwelt  upon.  The  fact  is  of  so  great  impor- 
tance that  it  may  well  be  restated  here  and  cannot  be  too  earnestly 
insisted  upon.  The  peculiar  carriage  of  the  head,  the  result  of  ano- 
phoria  or  of  declination,  is  beyond  question  a  most  important  element 
in  the  predisposition  to  tubercular  disease  of  the  lungs.  The  bacillus 
of  consumption  finds  no  rest  and  no  encouragement  to  indefinite  mul- 
tiplication in  the  chests  of  persons  whose  heads  are  habitually  thrown 
backward,  nor,  indeed,  in  the  lungs  of  those  whose  heads  are  not 
habitually  thrown  too  far  forward.  The  advantages  of  the  so-called 
fresh  air  treatment  and  a  great  deal  more  beside  can  be  secured  by 
the  proper  carriage  of  the  head  which  follows  at  once  on  a  successful 


CARRIAGE  OF  HEAD.  315 

correction  of  the  declination  or  of  the  anophoria.  In  such  correc- 
tions, important  in  themselves,  are  to  be  found  the  most  effective 
means,  not  only  of  prevention,  but  of  relief  from  the  most  general 
single  cause  of  destruction  of  human  life.  I  am  quite  aware  that 
these  statements  will  be  regarded  as  extreme  and  as  the  outgrowth 
of  too  restricted  attention  to  a  single  class  of  phenomena.  The  state- 
ments are  neither  extreme  nor  the  expression  of  narrow  views.  They 
are  well  considered  and  based,  not  only  on  correct  principles,  but 
upon  carefully  observed  facts  in  a  large  experience  continued  through 
many  years. 

With  the  opposite  carriage  of  the  head,  which  results  from 
katophoria  or  from  declination,  are  often  found  chronic  pains  in  the 
back  of  the  head  about  the  occipital  origin  of  the  trapezius  muscle, 
at  the  spine  of  the  seventh  cervical  vertebra,  and  between  the  shoul- 
der-blades. They  are  the  expressions  of  the  too  constant  tension  on 
muscles  of  the  back  demanded  in  the  adjustment  of  the  eyes. 

The  position  of  the  head  in  katophoria  is  well  illustrated  by  Fig. 
92.  This  is  from  a  photograph  of  a  case  which  came  under  rny 
observation  before  the  introduction  of  the  tropometer.  The  position 
of  the  eyes  was  determined  (if  the  term  is  appropriate  where  no  exact 
measurements  were  made)  by  the  apparent  rotations  as  seen  without 
the  aid  of  an  instrument. 

The  pose  as  shown  is  not  in  any  respect  exaggerated,  and  it  was 
this  .pose  which  led  to  the  observation  of  the  position  of  the  eyes. 

An  operation  for  relaxation  of  each  inferior  rectus  was  done, 
and  the  second  photograph  (Fig.  93)  shows  the  habitual  pose  a 
week  later.  The  change  was  so  remarkable  that  it  led  to  the  imme- 
diate completion  of  the  tropometer,  which  had  been  previously  com- 
menced, but  which,  on  account  of  some  difficulties  in  arranging  the 
details,  had  been  left  unfinished. 

It  is  interesting  to  add  that  the  woman,  who  had  been  subject 
to  very  frequent  and  very  severe  attacks  of  epilepsy,  had  no  more 
attacks  during  the  two  years  that  I  knew  of  her  condition.  Since 
then  I  have  had  no  information  regarding  her. 

So  far,  indeed,  does  this  effect  of  tension  extend  that  chronic 
spasmodic  conditions  arise,  as  in  torticollis,  which  have  the  initial 
cause  in  declination  and  which  are  in  some  cases  quickly  relieved  by 
appropriate  treatment  of  the  ocular  condition,  and  in  other  cases, 
where  the  declinations  are  extreme,  the  relief  comes,  but  only  as  a 
result  of  much  patience  and  skillful  management. 


316 


ANOMALIES  OF  MOTOR  MUSCLES. 


That  these  difficulties  of  adjustments  also  affect  distant  organs 
by  the  reduction  of  the  general  nervous  supply  is  no  less  true.  Hence, 
many  forms  of  nervous  manifestations,  which  are  the  signs  of  a  lack 
of  nervous  force  sufficient  to  perform  the  offices  of  a  special  organ  and 
at  the  same  time  answer  the  demands  of  the  rest  of  the  organism,  are 
not  in  general  local  diseases,  but  local  expressions  of  nervous  fatigue. 
If  anophoria  predisposes  to  imperfect  respiration,  dyspepsia  is  a  be- 
setting penalty  of  katophoria.1  A  single  suggestion  in  addition  is 
appropriate. 

A  class  of  causes  so  prolific  of  nervous  disturbances  may  extend 


iff.  110. 


Fig.  111. 


its  effects  beyond  the  mere  functional  manifestations.  That  nutrition 
may  be  disturbed  is  evident,  and  that  the  nutrition  of  nerve  centers 
may  be  so  modified  that  organic  changes  may  result,  it  is  reasonable 
to  assume. 

It  will  be  seen  that  the  person  represented  at  Fig.  110,  with  the 
long  head  (from  before  backward)  and  the  strong  angle  of  the  face, 
carries  the  forehead  quite  far  back  and  the  chin  well  up,  not  from 
any  affectation  of  attitude,  but  because  it  is  less  wearisome  to  the  eyes 
to  assume  this  position.  As  a  matter  of  fact  this  person's  eyes  were 
normally  adjusted  10°  below  the  plane  which  has  been  found  to  be  the 
best  and  which  may  be  called  the  standard  plane.  On  the  contrary 


1  See,  for  a  suggestive  explanation,  page  193. 


CARRIAGE  OF  HEAD. 


317 


the  young  girl  whose  pose  is  represented  at  Fig.  Ill,  whose  head  is 
high  compared  to  its  transverse  and  horizontal  diameters,  a  head 
which  is  neither  of  the  long  nor  hroad  type,  but  of  the  medium  (tall) 
type  with  the  absence  of  a  strong  angle  of  the  face,  had  the  plane  of 
vision  very  high.  Such  a  person  prefers  to  throw  the  forehead  in 
advance  and  the  chin  into  the  breast,  rather  than  make  a  continual 
and  somewhat  tiresome  effort  to  draw  the  eyes  to  the  proper  plane 
by  direct  tension  upon  the  depressor  muscles  of  the  eyes. 

It  is  not  difficult  to  see  that  this  selection  of  the  easiest  method 
of  adjusting  the  lines  of  sight  to  surrounding  objects  exercises  a  com- 
manding influence  on  the  whole  pose  of  the  body. 


r 


Fig.  112. 


Fig.  113. 


Attention  has  been  directed  to  the  fact  that  the  excessive  upward 
direction  of  the  plane  of  vision  is  found  principally  with  the  tall  or, 
more  technically,  the  mesocephalic  head.  Xot  only  is  the  pose  of  the 
head  and  body  modified  by  this  adjustment  of  the  eyes,  there  are 
marked  characteristics  of  facial  expression  due  to  the  same  cause. 
In  cases  of  these  high  adjustments  the  brows  are  compressed  and 
the  expression  is  one  of  intensity.  The  chin  is  not  elevated  as  in  the 
other  class,  but  the  forehead  is  advanced  and  the  body  leans  forward. 
The  shoulders  bend  forward  and  the  chest  is  often  compressed.  With 
the  noblest  form  of  the  head  often  comes  a  stoop  of  the  body.  Fortu- 
nately for  the  world  these  people  do  not  all  have  consumption,  for  if 
they  did  one  of  the  highest  forms  of  development  of  humanity  would 
be  wiped  out.  Unfortunately,  however,  it  is  from  this  class  of  people 
that  cocsumption  finds  the  great  majority  of  its  victims.  Glance  at 


318  ANOMALIES  OF  MOTOR  MUSCLES. 

the  position  of  the  air  passages  in  these  two  portraits,  in  each  of  which 
the  habitual  pose  of  the  body  and  head  is  fairly  represented. 

In  the  case  of  the  one  with  the  broad  head  and  difficult  upward 
rotations  of  the  eyes  (Fig.  112),  swarm  of  tubercle  bacilli  would  pass 
in  and  out  of  the  respiratory  passages  with  much  the  same  effect  as 
any  other  minute  particles  of  dust,  while  in  the  case  of  the  tall  headed 
boy  (Fig.  113)  who  has,  by  actual  measurement,  the  visual  plane 
adjusted  more  than  twenty  degrees  above  the  horizon,  the  larynx 
forms  a  hinge-like  valve  and  in  the  quiet  eddies  of  a  lung  under  these 
circumstances  the  tubercle  bacilli  can  easily  hold  high  carnival.  If 
the  direction  of  the  large  branches  of  the  air  tubes  is  considered  it  is 
evident  that  the  circulation  of  the  air  in  the  very  upper  portions  of 
the  lungs  of  one  with  such  a  habitual  pose  would  naturally  be  even 
less  active  than  in  the  lower  parts,  and  it  is  interesting  to  remember 
that  it  is  in  the  upper  lobes  that  the  bacilli  usually  commence  their 
inroads.  The  modern  treatment  of  consumption  is  fresh  air.  It  is 
evident  that  the  amount  of  air  admitted  to  the  lungs  of  a  person  with 
the  habitual  attitude  of  this  boy  must  be  very  materially  modified 
by  this  position  of  the  head ;  and  could  the  normal  pose  be  improved 
he  would  by  that  means  be  automatically  subjected  to  the  fresh-air 
treatment.  It  will  be  seen  that  this  is  entirely  practicable. 


SECTION  XLIV. 

FACIAL  EXPRESSIONS  RESULTING  FROM  THE  CONDITIONS  OF  THE 

EYE  MUSCLES. 

Among  the  obvious  phenomena  of  heterophoria  and  of  declination 
are  certain  forms  of  facial  expression  which  are  so  characteristic  as  to 
reveal  to  the  expert  at  a  glance  the  general  facts  in  regard  to  the 
existence  and  kind  of  the  anomaly.  Even  the  general  observer  when 
once  his  attention  has  been  called  to  these  characteristic  forms  of 
expression  is  able  to  make  a  fairly  accurate  estimate  of  the  under- 
lying conditions  of  adjustments  of  the  eyes. 

The  fact  that  such  habitual  and  normal  facial  expressions  are 
in  any  way  related  to  the  state  of  the  eye  muscles  in  health  was  first 
shown  by  myself  in  a  paper  published  in  Science,  May  6,  1892.  The 
subject  was  more  fully  discussed  in  an  article  in  Annales  d'Oculistique, 
October,  1892.  In  these  papers  only  the  expressions  incident  to  the 
different  forms  of  heterophoria  were  discussed.  Later  those  from 


FACIAL  EXPRESSIONS.  319 

declinations  were  pointed  out  in  my  contributions  to  the  subject  of 
declinations.1 

Space  in  this  work  does  not  permit  of  a  full  discussion  of  the 
important  phenomena  and  principles  involved  in  this  subject,  and 
only  a  summary  of  the  facts  can  be  here  given. 

As  it  is  elsewhere  stated  that  heterophoria  is  in  general  the  ex- 
pression of  the  efforts  of  adjustments  from  declinations,  it  is  obvious 
that  declinations  must  play  an  important  role  in  the  expressions  of 
heterophoria.  So  far  is  this  true  that  some  of  the  characteristic  ex- 
pressions at  first  attributed  to  certain  forms  of  heterophoria  are  in 
fact  those  of  declination  modified  by  the  heterophoric  state. 

Thus,  for  example,  hyperphoria  is  generally  characterized  by  a 
group  of  tensions  of  the  facial  muscles  which  is  often  very  striking. 
But  some  of  the  principal  elements  of  the  group  arise  directly  from 
the  declination  which  is  the  cause  of  the  hyperphoria,  while  others  are 
either  the  direct  results  of  the  latter  anomaly,  each  set  of  elements 


being  modified  as  the  result  of  the  two  conditions,  the  original  and 
the  secondary. 

Some  of  the  characteristic  expressions  of  declination  have  been 
already  referred  to  in  Section  XXVIII.  They  will  be  recalled  here 
in  order  to  associate  them  with  those  of  heterophoria. 

The  contour  of  the  brows  is  very  strongly  marked  with  most 
cases  of  important  declination.  Three  very  distinct  and  suggestive 
forms  are  observed  with  three  as  distinct  associated  forms  of  declina- 
tions. 

These  are,  first,  and  perhaps  the  most  common,  the  form  in 
which  one  brow  is  compressed  while  the  other  is  elevated  at  the  outer 
extremity.  The  diagram  (Fig.  114)  is  not  at  all  exaggerated.  It 
indicates  homonymous  declinations,  the  compressed  brow  being  over 


1  The  extreme  peculiarities  of  the  actions  of  the  facial  muscles  resulting 
from  paralysis  of  the  muscles  controlling  the  upper  eyelids  had  been  observed 
and  described.  The  expressions  arising  from  the  peculiarities  of  expression 
from  normal  adjustments  had  not,  previous  to  the  appearance  of  the  articles 
referred  to,  received  attention  in  any  publication. 


320  ANOMALIES  OF  MOTOR  MUSCLES. 

the  eye  with  the  positive  leaning  of  the  vertical  meridian,  the  slanting 
one  over  that  with  negative  declination.  There  is  often  associated 
with  such  a  combination  of  declinations  marked  hyperphoria,  and 
since  the  eye  with  the  positive  declination  is  that  the  visual  line  of 
which  tends  to  rise  above  the  other,  the  expression  becomes  a  part  of 
that  of  hyperphoria.  To  this  we  shall  return. 

Independently,  however,  of  any  manifest  hyperphoria,  there  is 
often  associated  with  this  form  of  expression  a  depression  of  the  posi- 
tion of  the  whole  eyeball.  This  expression  has  been  observed  by  others 
and  has  been  incorrectly  attributed  to  asymmetry  of  the  bony  struc- 
tures of  the  face  or  cranium.  Text-books  on  the  eye  have  published 
reproductions  of  photographs  of  such  asymmetrical  faces  and  an- 
atomists have  recognized  the  phenomenon.  Thus,  0.  Zoth  writes  to 
tli is  effect:1 

"When  the  head  is  in  the  primary  position  and  parallel  lines  of 
regard  are  directed  toward  the  horizon,  it  will  usually  happen  that 
the  centers  of  the  two  pupils  will  be  in  the  same  horizon.  This  is  not, 
however,  always  the  case,  since  variations  in  the  height  to  the  extent 
of  some  millimeters  occur  through  the  asymmetry  of  the  cranial  bones 
or  perhaps  also  of  the  soft  parts.  Still  more  important  differences 
are  found  in  the  asymmetry  of  the  (sagittal)  planes  of  the  skull,  so 
that  the  left  eye  usually  lies  several  millimeters  nearer  to  the  central 
(sagittal)  plane  than  does  the  right."  The  author  quotes,  in  this  con- 
nection, Hasse,  Arch,  fur  Anat.  und  Phys.  Anat.,  1887. 

Practical  experience  with  great  numbers  of  these  cases  has  shown 
me  that,  beyond  question,  the  false  location  of  the  depressed  eye  when 
it  is  associated  with  the  depression  of  the  brow,  is  the  direct  result  of 
the  muscular  tensions  brought  to  bear  in  the  automatic  correction  of 
the  tendency  of  the  meridians  to  tilt  in  the  positive  direction.  With 
a  corresponding  tendency  to  negative  declination,  the  eye  is  elevated. 

If  the  declination  is  corrected  by  suitable  operative  measures 
the  depressed  eye  rises  to  the  plane  of  the  other  and  no  longer  presses 
toward  the  median  plane.  The  illustrations  (Figs.  115  and  116) 
show  two  of  these  cases  of  asymmetrical  position  of  the  eyes  in  which 
the  +  declination  of  the  left  eye  was  in  each  case  pronounced,  while 
the  negative  declination  of  the  right  was  nearly  as  great. 

As  a  matter  of  fact  the  depression  of  the  eyeball  is  less  than 
appears,  for  in  nearly  all  these  cases  there  is  a  tendency  of  the  head 


1  In  Nagel's  "Handbuch  der  Physiologic  des  Menchen,"  1905,  iii,  p.  291. 


FACIAL  EXPRESSIONS. 


321 


to  lean  to  the  side  of  the  positive  declination,  while  it  is  also  some- 
what rotated  so  that  the  median  plane  is  directed  somewhat  to  the 
right.  In  both  the  cases  shown,  if  the  head  had  been  confined  exactly 
in  the  primary  position,  the  asymmetry  in  the  position  of  the  eye- 
ball would  have  been  less  conspicuous,  while  the  difference  in  the 
curve  of  the  brows  would  have  been  shown  to  be  no  less,  but  rather 
more  in  contrast. 


Fig.  115. 


Fi<r.  116. 


There  are  many  modifications  of  this  form  of  arrangement  of 
the  brows  depending  upon  the  degree  of  declination  for  each  eye, 
and  the  proportion  between  the  positive  and  negative  form  of  lean- 
ing of  the  meridian.  It  is  with  this  form  of  declination  that  we  have 
esophoria,  but  there  are  cases  in  which  there  is  slight  positive  declina- 
tion for  one  eye  and  much  more  decided  declination  of  the  same  form 
for  the  other,  or  in  which  there  is  no  apparent  declination  for  one 
and  pronounced  declination  for  the  other,  that  esophoria  is  also  to 
be  found.  If  there  is  distinct  anophoria,  the  expression  will  be  dis- 
tinctly modified  by  this  fact. 


Fig.  117. 

A  second  form  of  expression  about  the  brows  from  declination 
is  that  in  which  each  brow  slants  up  from  the  temporal  extremity 
and  terminates  almost  in  the  general  line  of  slant  at  the  median 
extremity.  Two  deep  ridges  usually  pass  from  the  inner  extremities 
of  the  brows  downward  in  adults.  This  form  is  seen  at  Fig.  117. 

It  is  associated  with  double  positive  declinations,  the  degree  of 
tilting  being  nearly  equal  for  the  two  eyes.  As  such  double  declina- 
tions are  conducive  to  exophoria,  this  form  of  brow  adjustment  is 
also  suggestive  of  exophoria,  but  since  exophoria  does  not  always 


322  ANOMALIES  OF  MOTOR  MUSCLES. 

4 

result  from  such  declinations  as  usually  induce  the  expression  alone, 
it  docs  not  prove  cxophoria. 

A  third  form  of  brow  contour  which  is  characteristic  is  that  in 
which  the  brows  are  each  elevated  toward  the  temple  and  each  has 
a  curve  similar  but  not  always  equal  to  its  fellow.  It  is  shown  at 
Fig.  118.  It  is,  like  the  form  shown  at  Fig.  117,  indicative  of  posi- 
tive declinations  of  each  eye,  but  of  quite  unequal  degrees.  Exo- 
phoria  is  more  commonly  found  with  this  expression,  but  when  the 
degree  of  positive  declination  of  one  eye  is  greatly  out  of  proportion 
to  the  other,  esophoria  results,  hence  the  expression  may  sometimes 
be  found  with  esophoria. 

It  is  evident  from  what  has  preceded  that  since  esophoria  or 
cxophoria  may  depend  on  the  proportional  degree  of  declinations  of 
the  two  eyes,  there  may  be  certain  modifications  of  facial  expressions 
in  each  of  these  forms  of  heterophoria. 

There  are,  notwithstanding  this,  certain  forms  of  expression 
which  are  typical  for  each  of  these  anomalies. 


Several  forms  of  expression  are  shown  at  pages  323  and  324, 
where  the  diagrams  represent  the  typical  adjustments  of  the  facial 
muscles  with  orthophoria,  esophoria,  exophoria,  and  hyperphoria. 

With  cases  of  permanent  orthophoria  there  is,  as  a  rule,  only 
slight  declination  of  either  eye;  there  is  therefore  no  heterophoric 
tendency  and  no  anomalous  tension  of  any  of  the  facial  muscles  in 
the  effort  to  correct  such  defects.  The  typical  expression  is  indi- 
cated at  Fig.  119. 

The  brows  are  neither  strongly  curved  nor  are  they  straight. 
They  do  not  point  upward  toward  the  temples  nor  toward  the  nose. 
The  curve  is  slight  and  equal  for  the  two  sides  of  the  face.  The  line 
of  the  mouth  is  horizontal,  being  neither  arched  toward  the  nose 
nor  downward.  It  is  usually  considerably  shorter  than  the  mouth 
of  an  exophoric  person.  The  lines  from  the  alae  of  the  nose  are 
neither  strongly  downward  nor  do  they  approach  too  much  the  hori- 
zontal. The  cheeks  are  neither  extended  nor  drawn  in,  hence  the 
face  is  oval  and  regular. 

Taking  the  face  in  all  its  elements,  there  is  an  expression  of  dis- 


FACIAL  EXPRESSIONS. 


323 


tinct  muscular  repose  compared  with  the  expression  of  any  form  of 
heterophoria.  This,  however,  does  not  prevent,  but  rather  encour- 
ages, a  free  play  of  the  facial  muscles,  and  the  expression  is  not  only 
vivacious  but  agreeable. 

The  most  characteristic  expression  of  esophoria  is  that  shown 
at  Fig.  120.  Esophoria  is  very  frequently  associated  with  anophoria, 
in  which  condition,  as  shown  in  the  figure,  the  brows  are  generally 
compressed.  With  this  depression  there  is  the  unequal  direction  of 
the  brows  characteristic  of  declination.  The  eyes  are  not  fully  open 
and  the  upper  lid  is  nearly  hidden.  The  mouth  generally  curves 
upward  at  the  middle,  the  cheeks  are  protruding,  the  lines  from  the 


alas  are  more  horizontal  than  they  are  in  orthophoria.  On  the  whole, 
there  is  in  this  expression  a  suggestion  of  tension  of  the  muscles  of 
the  face,  with  partly  closed  eyes,  full  cheeks,  and  horizontal  lines. 
The  deep  vertical  lines  which  occur  just  above  the  root  of  the  nose 
and  the  horizontal  lines  low  on  the  forehead  add  special  features  to 
the  picture. 

With  exophoria  we  have  a  marked  contrast  to  the  ensemble  of 
expressions  of  esophoria. 

The  most  typical  form  of  exophoric  expression  is  that  shown  at 
Fig.  121. 

Exophoria  is  often  associated  with  katophoria,  and  hence  we 
have  more  frequently  the  elevated  brows. 

The  brows  may  have  the  form  shown  in  the  diagram  at  Fig.  117, 


324 


ANOMALIES  OF  MOTOR  MUSCLES. 


high  at  the  center  and  sloping  slightly  each  way,  or  either  of  the 
forms  seen  at  Figs.  118  or  121.  That  shown  in  the  diagram  (Fig. 
121)  is  perhaps  most  common.  The  eyelids  are  conspicuous,  not 
because  they  droop,  but  because  the  tissues  above  are  drawn  away  from 
them.  The  mouth  curves  downward  at  the  middle  and  is  long,  the 
frenum  of  the  upper  lid  is  long.  The  lines  from  the  ala9  of  the  nose 
descend  abruptly,  and  the  cheeks  are  drawn  in,  giving  the  face  an 
appearance  of  length.  With  the  form  of  eyebrows  seen  at  Fig.  117 
the  face  is  broader  and  the  lines  less  vertical.  In  the  typical  form 
as  seen  at  Fig.  121,  the  horizontal  lines  of  the  forehead  are  higher 


Fig:.   121. 


than  those  of  esophoria.  In  adult  age,  and  especially  in  advanced 
age,  the  exophoric  expression,  or  more  exactly  the  double  -|-  declina- 
tion expression,  becomes  so  pronounced  that  the  elevation  of  the 
brows  and  the  depression  of  the  eyelids,  as  they  press  against  the  eyes 
to  aid  in  holding  the  eyes  in  position,  leads  to  the  supposition  that 
a  condition  of  ptosis  exists.  Quite  on  the  contrary,  the  eyelids  were 
performing  unusual  duty. 

The  typical  expression  from  hyperphoria  is  even  more  character- 
istic than  the  others.  The  fact  of  the  existence  of  very  pronounced 
declination  aids  in  the  peculiarities  of  the  muscular  tensions.  The 
unsymmetrical  features  shown  at  Fig.  122  are  the  normal  results 
of  the  conditions  leading  to  hyperphoria  and  the  fact  of  hyper- 
phoria itself.  The  diagram  shows  the  compressed  brow  on  one  side 


FACIAL  EXPRESSIONS.  325 

and  the  elevated  one  on  the  other.  By  compression  the  brow  aids  in 
preventing  the  deviation  of  the  visual  line  of  that  eye  above  the 
other.  The  elevation  of  the  other  brow  removes  pressure,  permitting 
the  lower  inclined  visual  line  to  be  raised.  Thus,  the  expression  of 
declination  and  that  of  hyperphoria  coincide  so  far  as  the  brows  are 
concerned.  But  the  whole  face  enters  into  the  effort  to  avoid  diplopia. 
On  the  side  of  the  compressed  brow  the  corner  of  the  mouth  is  raised 
and  on  the  side  of  the  elevated  brow  the  mouth  is  depressed.  Thus 
one  side  of  the  face  appears  longer  than  the  other.  A  curved  ridge 
in  the  skin  or  a  series  of  ridges  is  shown  above  the  elevated  brow, 
and  the  frenum  of  the  upper  lip  is  drawn  toward  the  depressed  end 
of  the  mouth.  Thus  there  is  a  marked  appearance  of  a  want  of  sym- 
metry of  the  two  sides  of  the  face.  The  head  is  generally  held  on 
one  side,  leaning  toward  the  shoulder  of  the  side  on  which  the  brow 
is  compressed  and  compensating  leanings  of  the  body.  This  form 
of  expression  has  more  than  once,  in  scientific  works,  been  figured 
as  an  example  of  unsymmetrical  formation  of  the  brows,  of  the  head 
and  face.  It  is  interesting  to  note,  however,  that  immediately  on  a 
successful  correction  of  the  declination,  and  consequently  of  the 
hyperphoria,  the  whole  face  becomes  symmetrical. 

A  study  of  the  muscular  causes  of  these  peculiarities  of  expres- 
sion is  extremely  interesting,  but  I  must  refer  the  reader  to  my  essay 
"Les  Muscles  Moteurs  de  FOeil  et  1'Expression  du  Yisage"  in  An- 
nales  d'Oculistique,  October,  1892,  for  a  full  discussion  of  the  causes 
of  each  form  which  I  have  here  mentioned. 

A  single  question  remains  to  be  answered  here.  Will  a  correction 
of  the  existing  heterophoria  or  the  declination  serve  to  modify  the 
expression,  rendering  it  more  regiilar  in  repose  and  more  agreeable? 
The  most  positive  affirmative  reply  can  be  given  to  this  question. 
This  work  is  not  intended  as  a  medium  for  reporting  cases,  but  with 
a  view  of  illustrating  the  satisfactory  and  often  even  surprising  results 
which  may  be  expected,  a  few  contrasting  pictures  are  here  intro- 
duced. It  should  be  said  that  in  each  instance  the  photograph  indi- 
cates, not  some  momentarily  strained  expression  either  for  better  or 
worse,  but  shows  the  passive  and  customary  expression  without  sug- 
gestion and  without  special  posing.  Also,  it  should  be  said  that  in  no 
instance  has  the  negative  been  in  any  sense  retouched  or  improved. 
The  portraits  are  from  the  negatives  as  they  came  from  the  camera 
and  the  developing  bath.  If  one  should  suggest  that  the  same  person 
may  at  one  time  show  greater  repose  of  features  than  at  another,  I 


326 


ANOMALIES  OF  MOTOR  MUSCLES. 


reply  that  these  contrasting  portraits  show,  not  occasional  and  acci- 
dental improvements,  they  simply  illustrate  a  rule — a  rule  which, 
when  the  conditions  of  relief  to  the  declination  and  heterophoria  are 
fulfilled,  is  as  uniform  in  its  action  as  any  in  physiology. 

Figs.  123  and  124  represent  a  young  girl  with  epilepsy  who  had 
a  high  degree  of  esophoria.  It  will  be  seen  at  Fig.  123  that  the  entire 
expression  of  the  face  agrees  with  the  diagram  (Fig.  120). 


Fig.  123. 


Fig.  124. 


There  are  the  compressed  brows,  but  it  is  easy  to  see  that  the 
right  is  compressed  much  more  than  the  left.  The  two  creases  be- 
tween the  brows,  the  shortened  lip,  the  fullness  of  the  cheeks,  the 
compression  above  the  eyelids,  nearly  concealing  them,  all  go  to  make 
a  picture  of  esophoria. 


Fig.  125. 


Fig.  126. 


Three  weeks  later,  when  the  esophoria  had  been  relieved  by  op- 
eration, the  second  photograph  was  taken  (Fig.  124).  Here  there 
is  an  absence  of  tension  of  the  face;  the  brows  are  raised  equally,  the 
overhanging  tissues  no  longer  conceal  the  lids,  the  eyes  are  more  open, 
the  lip  is  not  contracted,  and  the  lines  between  the  brows  are  gone. 
It  is  pleasant  to  add  that  the  girl  has  been  well  of  epilepsy  since  these 
photographs  were  taken,  ten  years  ago. 

Figs.  125  and  126  show  the  typical  expression  of  exophoria  in  a 


GENERAL  TREATMENT.  327 

lady.  It  is  easy  to  see  in  Fig.  125  the  elevated  brows,  the  exposed 
eyelids,  the  long  mouth  depressed  at  the  center,  the  drawing  in  of 
the  cheeks,  in  fact,  a  picture  of  exophoria.  The  exophoria  was  re- 
lieved by  operation  before  the  conditions  of  declination  had  been 
studied.  The  second  photograph  (Fig.  126),  taken  some  months 
later,  shows  the  modifying  influence  of  the  correction,  although  sub- 
sequent examinations  have  shown  important  declinations,  the  exist- 
ence of  which  could  well  be  assumed  by  one  accustomed  to  observe 
these  expressions. 

Figs.   127  and  128  represent  a  lad  with  hyperexophoria.     Fig. 
127  shows  the  habitual  expression  of  the  boy  before  the  defect  was 


Fig.  127.  Fig.  128. 

• 

corrected.     Fig.  128  shows  equally  the  habitual  expression  after  the 
correction  of  the  hyperphoria  only. 

These  contrasts  are  not  unusual  or  exceptional;  they  are,  as 
has  already  been  said,  the  rule.  They  illustrate  the  influence  of  the 
tensions  of  the  eye  muscles  on  all  the  muscles  of  the  face. 


SECTION  XLV. 

TREATMENT  OF  NOX-STRABISMIC  ANOMALIES    (ANOPHORIA, 
KATOPHORIA,  HETEROPHORIA  AND  DECLINATION). 

GENERAL  TREATMENT. 

The  treatment  which  may  be  called  "general  treatment,"  that 
Is,  treatment  directed  to  the  general  physical  condition  of  the  pa- 
tient, need  not  be  considered  separately  for  the  different  anomalies 
thus  far  discussed,  since  it  is  the  same  for  all. 

It  will  not  be  supposed  by  any  one  who  has  dftly  considered  the 
subject  that  the  conditions  described  are  essentially  amenable  to  any 


328  ANOMALIES  OF  MOTOR  MUSCLES. 

"general"  treatment.  They  are  all  conditions  depending  directly 
upon  anatomical  peculiarities,  and  cannot  be  changed  by  medical  or 
other  treatment  directed  to  general  physical  conditions. 

Notwithstanding  this,  much  temporary  benefit  may  result  from 
well-considered  treatment  of  this  nature. 

These  conditions,  anatomical  as  they  are,  are  nevertheless  such 
as  may  be  supported,  often  without  marked  suffering  or  even  con- 
scious inconvenience,  provided  the  general  forces  of  the  system  are 
ample  and  the  parts  engaged  in  overcoming  the  defect  are  not  dis- 
abled by  fatigue.  In  childhood  and  early  youth  the  effects  of  most 
of  the  conditions  of  these  classes  are  unobserved.  The  great  elasticity 
of  tissues,  the  affluence  of  surplus  energy,  and  the  comparatively 
moderate  demand  upon  the  adjusting  powers  of  the  eyes,  all  con- 
tribute to  a  comparative  degree  of  immunity  from  the  unpleasant 
effects  which  may  be  experienced  after  the  more  severe  duties  of 
school  or  of  active  life  have  made  greater  demands,  or  after  sick- 
ness has  reduced  the  surplus  of  nervous  capital. 

Such  facts  are  eminently  suggestive  in  regard  to  the  relief  which 
may  be  hoped  for  when  the  local  or  general  effects  of  these  unfavor- 
able eye  adjustments  are  present. 

The  child  whose  face  or  whose  shoulders  exhibit  the  convulsive 
movements  of  chorea,  the  mother  who  suffers  from  oft-recurring 
headaches,  and  the  student  who  suffers  from  asthenopia  are  all,  most 
frequently,  examples  of  the  fact  that  in  the  case  of  each  the  expense 
of  ocular  adjustments  is  greater  than  the  victim  is  able  to  afford. 
The  natural  and  logical  course  would  be  in  each  case  the  institution 
of  a  greater  economy,  first  in  the  employment  of  the  parts  directly 
employed  in  these  adjustments,  and  then  in  the  general  expenditure 
of  nervous  energy. 

In  short,  the  remedy  which  suggests  itself  first  and  most  forcibly 
is  rest. 

The  choreic  child  removed  from  school,  the  tired  mother  relieved 
of  her  duties,  and  the  student  sent  on  a  vacation  may  each  get  better 
of  the  nervous  complaint.  In  each  case  the  trouble  may  return 
when  the  abandoned  duties  are  resumed,  but  at  least  there  is  tem- 
porary relief  in  a  great  many  cases.  During  such  temporary  relief 
the  general  physical  tone  may  so  greatly  improve  that  freedom  from 
the  disturbances  to  health  may  be  gained  for  a  certain  time.  Eest 
will  not  remove  the  anomaly  nor  will  it  render  the  demand  upon  the 
nervous  forces  in  adjustment  any  less.  It  will  permit  the  nervous 


GENERAL  TREATMENT.  329 

energies  to  be  renewed  and  thus  enable  the  patient  to  overcome  his 
defect. 

Something  more  than  this  may  be  required.  The  general  "tone" 
of  the  individual  may  have  become  so  low  that  treatment  directed  to 
its  reestablishment  may  be  required.  Among  the  instrumentalities  to 
this  end  are  tonic  medicines,  a  change  of  air,  and,  better  than  either, 
a  change  of  surroundings.  Tonics,  fresh  air,  wholesome  and  abun- 
dant food,  and  travel  constitute  the  principal  means  for  reestablish- 
ing the  general  vigor  of  the  nervous  organism. 

Even  the  abstinence  from  accustomed  labor  and  the  use  of  the 
tonics  above  mentioned  may  fail  to  bring  relief,  because  the  muscles 
of  adjustment,  having  become  irritable  and  exhausted,  are  unable  to 
return  to  their  normal  state,  notwithstanding  all  these  things. 

As  a  local  stimulant  electricity,  judiciously  applied,  may  serve 
a  good  purpose.  There  is  much  fallacy  in  vogue  popularly,  and  even 
among  physicians,  in  regard  to  the  role  played  by  electricity  in  such 
cases.  It  is  a  delusion  to  suppose  that  electricity  and  nerve  energy 
are  here  convertible  forces,  that  by  passing  the  current  of  one  through 
a  portion  of  the  body  a  supply  of  the  other  is  furnished.  Electricity, 
thf  faradic  current,  stimulates  the  action  of  the  nerves,  bringing 
into  active  and  unusual  movement  the  forces  which  are  already  pre- 
pared. This  active  and  unusual  movement  may  induce  a  change  of 
nutrition,  of  metabolism,  or  establish  a  new  way  for  the  action  of 
the  nervous  powers  possessed  by  the  individual. 

The  passing  of  a  weak  faradic  current  through  the  orbits  three 
or  four  minutes  daily  for  a  few  days  may  prove  a  decided  relief  to 
many  cases  of  nervous  disturbance  arising  from  the  difficulties  of 
ocular  adjustments. 

Before  leaving  the  consideration  of  these  constitutional  or  gen- 
eral methods  of  treatment,  it  is  important  to  mention  some  of  the 
things  which  should  not  be  done. 

Among  the  symptoms  induced  by  the  anomalies  under  consid- 
eration, the  most  common  perhaps  are  headaches,  neuralgia,  insom- 
nia, and  asthenopia.  All  these  are  painful  or  distressing,  and  in  the 
case  of  all  it  is  relief  for  which  the  patient  asks.  It  has  been  of  late 
years  customary  to  obtain  such  relief  by  the  administration  of  cer- 
tain coal-tar  preparations,  such  as  sulphonal,  chloral,  etc.  An  im- 
mediate relief  is  often  gained  and  sleep  is  induced,  hence,  there 
appears  to  the  patient  no  reason  why  the  remedy  should  not  be 
repeated  whenever  the  pain  returns. 


330  ANOMALIES  OF  MOTOR  MUSCLES. 

It  should,  however,  be  borne  in  mind  that  these  drugs  are  all 
paralyzers.  The  relief  gained  is  unlike  the  relief  gained  from  an 
opiate,  and  the  muscles  which  have  been  the  origin  of  the  trouble 
are,  following  a  dose  of  sulphonal  or  chloral,  less  able  to  accomplish 
their  function  than  before.  From  the  clinical  point  of  view,  the 
effect  of  this  class  of  drugs  appears  to  be  that  of  paralyzers  of  the 
nuclear  region  supplying  the  nerves  of  the  eye  muscles.  This  being 
the  case,  the  administration  of  medicines  of  this  class,  while  possibly 
affording  immediate  relief,  lays  the  foundation  for  more  frequent 
and  more  serious  manifestations  of  the  nervous  trouble,  and  tem- 
porary relief  is  given  at  the  expense  of  more  lasting  injury. 

]\Iore  than  twenty  years  ago  I  observed  that  after  using  drugs 
of  this  class  (chloral  was  the  representative  of  the  class  at  that  time) 
the  eye  muscles  were  in  a  state  of  mild  paresis  and  that  the  tests  for 
heterophoric  conditions  were  unreliable.  Abundant  observation  has 
shown  that  these  drugs  are  most  pernicious  in  their  action  in  all 
cases  of  nervous  disturbance  arising  from  anomalous  states  of  the 
eye  muscles.1 


THE  USE  OF  PRISMS. 

Coming  to  the  more  direct  agencies  through  which  relief  from 
the  functional  disturbances  arising  from  the  action  of  the  eye  mus-" 
cles  may  be  gained,  the  use  of  prisms  will  be  first  mentioned.  They 
may  be  used  either  as  instrumentalities  by  means  of  which  certain 
exercises  of  a  gymnastic  character  can  be  accomplished,  or  they  can, 
by  virtue  of  their  refractive  character,  be  used  as  spectacles  to  be 
worn  habitually. 

The  employment  of  prisms  as  a  means  of  gymnastic  exercise 
was  suggested  by  von  Graefe,  but  was  little  used  by  him.  Yon 
Graefe's  pupil  and  disciple,  Soelburg  Wells,  in  his  admirable  work 
on  the  diseases  of  the  eye,  recommended  exercises  by  prisms,  ad- 
vising that  the  patient  look  at  a  wand  or  other  object  six  feet  in  front 
of  him  and  try  to  overcome  prisms.  Xo  very  systematic  method, 
however,  was  adopted. 


1  Dr.  Arthur  A.  Boyer,  who  was  for  a  number  of  years  my  assistant,  pub- 
lished a  valuable  study  of  the  effects  of  these  drugs  under  the  title.  "A  Study 
of  Some  of  the  Drugs  Used  in  Functional  Nervous  Disorders''  (Journal  of 
Nervous  and  Mental  Diseases,  February,  1893). 


USE  OF  PRISMS.  331 

In  my  own  practice  I  gave,  many  years  ago,1  much  attention  to 
this  kind  of  exercise  and  reduced  it  to  a  more  orderly  procedure.  It 
was  one  of  the  means  by  which  many  of  my  earlier  reported  cases  of 
neuroses  treated  for  ocular  defects  were  relieved. 

I  reproduce  here,  in  substance,  the  method  described  in  one  of 
my  publications  as  practiced  in  the  early  stages  of  my  work  in  this 
field.2 

''The  patient  looking  at  the  flame  of  a  candle  at  twenty  feet 
distance,  a  weak  prism  is  placed,  base  out,  before  one  of  the  eyes. 
As  soon  as  the  images  unite,  an  equal  prism,  with  its  base  also  out, 
is  placed  before  the  other  eye.  As  fast  as  images  are  united  this 
alternate  addition  of  prisms  is  continued,  until  it  is  no  longer  con- 
venient to  add  to  them  or  until  the  patient  fails  to  unite.  Then,  if 
union  cannot  take  place,  the  prisms  are  removed  and  the  same  process 
is  repeated  until  more  can  be  accomplished,  if  possible. 

"If  the  patient  is  able  to  unite  these  weak  prisms  the  surgeon 
begins  with  those  of  higher  grade,  adding  alternately  until  the  images 
are  no  longer  united.  This  is  also  repeated  several  times. 

"By  this  means  the  adducting  ability  may  be  raised,  after  a  few 
exercises,  to  a  much  greater  degree  than  at  first  existed. 

"The  exercise  should  not  be  continued  more  than  five  or  six  min- 
utes. 

"A  similar  method  can  be  used  in  overcoming  by  abduction,  the 
prisms  being  placed  with  their  bases  in.  In  this  case  it  is  rarely 
required  to  add  one  prism  above  another  before  both  eyes,  a  single 
prism  before  one  eye  serving  the  purpose." 


GYMNASTICS  FOR  DECLIXATION. 

In  connection  with  the  subject  of  gymnastics  with  prisms,  exer- 
cises of  an  analogous  character  may  be  described,  which  can  be  done 
ill  cases  of  anomalous  declinations  by  means  of  small  glass  rods,  such 
as  Maddox  has  suggested  for  testing  in  heterophoria. 

Placing  in  the  trial  frames  one  of  the  disks  carrying  a  rod  for 
each  eye,  the  patient  unites  the  images  of  a  candle  flame.  The  rods 
are  then  rotated  out  and  in,  the  patient  holding  the  union  as  long  as 
possible  as  it  rotates  each  way.  A  little  instrument,  which  I  de- 


1  In  papers  published  in  1878  and  1879  these  exercises  were  described. 

2  "Memoire  Addresse  a  1'Academie  Royale  de  Medecine  de  Belgique,"  par 
George  T.  Stevens,  1883. 


332  ANOMALIES  OF  MOTOR  MUSCLES. 

scribed,1  and  which  I  called'  the  rod  clinoscope,  serves  very  well  for 
this  purpose,  and  permits  of  determining  the  extent  of  the  adjust- 
ments which  can  be  made. 

The  instrument  is  not  of  practical  value  for  determination  of 
the  degree  of  declination.  In  use  it  is  hung  from  the  arm  of  the 
phorometer. 


Fig.  129. — The  Rod  Clinoscope. 

The  measurements  of  the  rotations  by  this  means  are  not  alto- 
gether satisfactory,  partly  because  the  length  and  illy-defined  borders 
of  the  lines  of  light  render  it  difficult  to  form  a  correct  judgment  as 
to  the  perfect  union. 

By  far  the  best  means  of  arriving  at  a  satisfactory  knowledge 
of  the  rotations  around  the  line  of  regard  is  that  afforded  by  the 
tubular  clinoscope. 

Eemoving  the  haploscopic  fractional  diagrams  which  are  essen- 


Fig.  130. — Objectives  for  Clinoscope. 

tial  in  the  primary  use  of  the  instrument,  a  disk  with  a  single  straight 
line  extending  from  top  to  bottom  is  placed  in  each  tube.  (Fig.  130.) 
The  sharpness  of  definition  of  the  line  and  the  fact  that  it  does  not 
extend  too  far  in  the  field  of  regard  enable  the  observer  to  deter- 
mine very  closely  the  extent  of  the  revolution.  For  purposes  of 
scientific  examination  this  method  is  essential,  that  by 'the  streak  of 


1  Ophthalmic  Record,  May,  1898. 


PRISMS  AS  SPECTACLES.  333 

light  being  altogether  too  vague.  As  in  the  case  of  the  rods,  the 
clinoscope  tubes  may  be  rotated,  first  in  one,  then  in  the  other  direc- 
tion as  long  as  the  vertical  lines  are  held  in  union.  Only  a  few 
minutes  should  be  allowed  to  such  an  exercise.  It  need  not  be  said 
that  such  exercises  do  not  in  any  degree  correct  any  of  the  actual 
declination,  but  they  may  possibly  in  some  instances  afford  a  tem- 
porary relief  to  some  of  the  symptomatic  manifestations. 


PRISMS  WORN  AS  SPECTACLES. 

Prisms  may  be  used  as  spectacles  for  the  correction  of  the  tension 
induced  by  the  different  forms  of  heterophoria  or  for  ano-  or  kato- 
phoria. 

For  heterophoria,  prisms  which  together  correct  rather  less  than 
the  degree  of  the  defect  should  be  used,  and  a  prism  exceeding  3° 
before  one  eye  is  rarely  of  any  service.  The  instances  in  which  per- 
sons use  very  strong  prisms  with  supposed  benefit  are  generally  those 
in  whom,  when  the  attention  is  withdrawn  from  the  efforts  to  unite, 
images  are  thrown  even  farther  apart  than  they  would  be  without 
the  glasses. 

It  is  a  safe  rule  to  say  that  a  prism  exceeding  3°  is,  for  the  pur- 
pose of  spectacles,  worse  than  useless. 

Many  years  since  I  introduced  the  method  of  using  temporary 
prisms  in  the  progress  of  investigating  the  latent  heterophoria.  I 
had  prisms  of  1°,  2°,  3°,  and  4°  made  by  the  gross  and  frames  to 
match.  In  these  frames  any  prism  could  be  adjusted  in  a  moment. 
It  was  my  custom  to  loan  these  glasses  to  patients,  some  of  whom 
used  them  for  many  weeks.  My  experience,  in  watching  from  week 
to  week  a  great  number  of  persons  thus  using  prisms  which  were 
carefully  adjusted  and  never  sufficient  to  correct  the  manifest  trouble 
within  one  or  two  degrees,  convinced  me  that  the  cases  in  which  any 
important  relief  is  derived  from  the  wearing  of  prisms  is  extremely 
rare.  That  a  few  persons  do  find  temporary  relief,  and  a  smaller 
number  somewhat  permanent  relief,  is  true,  but  the  proportion,  corn- 
compared  with  those  who  gain  no  relief  is  small.  This  statement 
is  made  from  an  experience  doubtless  greater  than  has  been  presented 
to  any  other  observer,  and  is  made  without  reservation. 

In  anophoria  and  katophoria  I  have  found  a  larger  proportion  of 
cases  in  which  comparative  relief  has  been  afforded  than  in  hetero- 


334  ANOMALIES  OF  MOTOR  MUSCLES. 

phoria.  In  these  conditions  the  prisms  may  be  of  equal  strength  up 
to  3°  with  their  bases  up  for  katophoria  or  down  for  anophoria. 
Xext  in  the  order  of  proportional  relief  are  cases  of  moderate  hyper- 
phoria,  1°  or  l1/^0- 

In  the  employment  of  prisms  for  hyperphoria  cart  should  be 
exercised  to  place  the  prism  in  conformity  with  the  normal  direction 
of  the  optic  axes  in  respect  to  the  horizon.  If  the  hyperphoria  is 
associated  with  anophoria  the  base  of  the  prism  should  be  down 
before  the  eye  whose  visual  line  tends  to  rise  above  the  other.  If 
there  is  right  hyperphoria  with  anophoria,  place  the  prism  before  the 
right  eye  with  the  base  down,  or,  if  the  relief  is  to  extend  to  the  ano- 
phoria, place  a  prism  before  each  eye  with  the  base  down,  but  with 
the  prism  before  the  right  eye  stronger  than  that  before  the  left. 
The  same  principle  holds  in  katophoria;  the  base  of  the  prism  should 
in  this  case  be  up,  and  if  the  hyperphoria  is  right,  the  strongest  prism 
should  be  before  the  left  eye. 


DECENTERING   OF   SPHERICAL  AND   CYLINDRICAL   GLASSES   FOR 
OBTAINING  PRISMATIC  EFFECT. 

Every  spherical  and  cylindrical  glass  consists  essentially  of  an 
infinite  number  of  prisms.  In  the  case  of  the  cylinder  the  prisms 
only  extend  in  the  direction  at  right  angles  to  the  axis,  but  in  that 
of  the  spherical  lens  the  prism  influence  extends  in  every  direction 
from  the  optical  center. 

NOTE. — According  to  the  suggestion  of  Mr.  Charles  F.  Prentice  the  unit 
for  the  measurement  of  prisms  is  a  tangential  deviation  of  one  centimeter 
measured  in  a  plane  situated  at  one  meter  distance  from  the  prism,  without 
considering  the  angle  of  the  glass  or  the  index  of  refraction.  This  unit  he 
calls  a  prismatic  diopter  or  dioptric  prism.  According  to  this  calculation: 

One  diopter  prism  corresponds  to  a  tangential  deviation  of  1  centi- 
meter at  a  distance  of  1  meter. 

Two  diopter  prism  corresponds  to  a  tangential  deviation  of  2  centimeters 
at  a  distance  of  1  meter. 

Five  diopter  prism  corresponds  to  a  tangential  deviation  of  5  centi- 
meters at  1  meter  distance,  etc. 

This  method  of  graduation  of  prisms  has  many  advantages,  among  which 
are  that  the  unit  corresponds  with  the  unit  of  spherical  and  cylindrical  glasses 
as  now  numbered  and  that  the  prismatic  power  to  be  obtained  by  decentering 
spherical  glasses  numbered  in  diopters  is  perfectly  easy  to  determine. 

For  example,  a  spherical  convex  lens  of  1  diopter  has  its  focal  distance 
at  1  meter.  That  is,  rays  passing  through  any  part  of  the  lens  pass  either 


DECENTERING  GLASSES. 


335 


without  deflection  or  with  such  deflection  as  is  necessary  to  unite  all  at  the 
distance  of  1  meter  in  the  plane  of  the  axis  of  the  lens.  If  the  ray  passes 
parallel  to  the  axis  of  the  lens  of  1  diopter,  at  a  distance  of  1  centimeter  from 
the  optical  center  it  will  be  deflected  to  the  extent  of  meeting  the  axial  line  of 
the  lens  at  a  distance  of  1  meter,  hence  the  decentering  of  a  lens  of  1  D 
spherical  1  centimeter  is  equal  to  producing  an  effect  of  1  D  prism.1 

In  practice  the  most  convenient  and  most  satisfactory  manner 
for  determining  the  distances  between  the  optical  centers  of  spec- 
tacles of  spherical  lenses  in  order  that  they  shall  have  the  desired 
effect  as  prisms,  or  in  order  that  they  shall  have  no  prismatic  effect, 


IPrii-ZB. 


Fig.  131. — Diagram  Illustrating  Decentering  of  Lens  for 
Prismatic  Effect. 


is  that  of  adjusting  the  trial  glasses  by  the  aid  of  the  phorometer. 
This  is  accomplished  as  follows : — 

Having  determined  the  character  and  strength  of  the  refracting 
glass  for  each  eye  for  distance,  these  glasses  are  placed  in  the  trial 
frames  and  put  before  the  eyes  of  the  patient  so  that  the  optical 
centers  will  be  at  the  level  of  the  pupils.  Then  placing  the  phorome- 
ter in  position,  its  prisms  are  rotated  to  the  vertical  position  indi- 


1  For  a  full  discussion  of  the  siibject  of  the  prism  diopter,  see  a  paper  by 
Mr.  Charles  F.  Prentice  and  a  note  on  the  application  of  the  metric  system  to 
numbering  of  prisms  by  George  T.  Stevens,  in  Annales  d'Oculistique,  July,  1892. 


336  ANOMALIES  OF  MOTOR  MUSCLES. 

eating  0°.  The  patient  looks  at  the  candle  flame,  seeing  the  t\vo 
images.  If  one  image  is  not  vertically  over  the  other  the  phorometer 
maintains  the  same  adjustment,  but,  by  means  of  the  screw  connected 
with  the  trial  frame,  the  glasses  are  to  be  moved  out  or  in  until  the 
two  images  of  the  flame  are  exactly  in  the  same  vertical  line.  Of 
course,  if  the  glasses  are  of  strength  insufficient  to  do  this  without 
such  decentering  as  to  give  to  a  spherical  lens  a  different  character, 
the  object  can  only  be  accomplished  by  combining  a  prism  with  the 
spherical  lens. 

When  the  exact  point  is  reached  at  which  there  is  neither  eso- 
phoria  nor  exophoria,  the  distance  between  the  centers  of  the  lenses 
is  measured  and  this  distance  becomes  a  part  of  the  prescription  to 
the  optician  which  is  to  be  observed  in  making  the  spectacles. 

If  the  glasses  are  for  reading  only,  a  modification  of  this  method 
is  required,  for  glasses  which  at  near  points  would  bring  the  images 
in  line  at  the  reading  point  would,  in  some  instances,  cause  a  practical 
esophoria. 

In  this  case,  after  choosing  the  glasses,  they  are  to  be  placed  as 
before  in  the  trial  frame  and  in  the  proper  relation  to  the  eyes.  Then 
the  phorometer  is  to  be  brought  dose  to  the  eyes  and  set  at  about  5° 
exophoria.  By  turning  the  screw  of  the  trial  frames  the  images  of  a 
dot  or  small  cross  on  a  card,  which  is  held  at  reading  distance,  are 
brought  to  the  vertical  position,  and  the  distances  between  the  optical 
centers  measured  as  before.  In  making  this  test  the  line  of  von 
Graefe  through  the  dot  is  to  be  avoided,  since,  except  in  cases  of 
moderate  squint,  the  patient  will  hold  the  images  in  position  when 
there  is  a  line  for  guidance. 


SECTION  XLVI. 

SURGICAL  TREATMENT. 

While  it  is  to  be  admitted  that  medicines  which  promote  the  gen- 
eral vigor  of  the  individual  must  be  of  value,  that  a  change  of  air 
and  of  environment  exert  influences  which  are  favorable,  and  that 
pleasing  emotions  and  hopeful  encouragements  serve  to  promote  the 
well-being  of  patients  suffering  from  neuroses  which  have  their  origin 
in  ocular  disabilities,  it  is  evident  that  the  conditions  which  have 
served  to  induce  the  neuroses  are  not  removed  by  any  of  these  means. 

The  teaching  of  von  Graefe  in  this  connection  is  extremely  ap~ 


SURGICAL  TREATMENT.  337 

propriate.  In  speaking  of  the  treatment  of  asthenopia  by  means 
which  are  not  radical,  he  says: — 

"In  these  cases  of  temporary  asthenopia,  fresh  air,  cold  water, 
tonic  medicines,  and  electricity  are  indicated.  What  disappears  under 
such  treatment  is  only  the  symptom  of  asthenopia,  while  the  disturb- 
ance of  the  equilibrium  of  the  antagonistic  muscles  remains  and  the 
least  sinking  of  energy  recalls  the  former  difficulties."1 

Just  as  the  local  symptom  asthenopia  may  disappear  for  the 
time  under  the  influence  of  rest  and  tonics,  the  more  distant  nervous 
reactions  arising  from  the  class  of  causes,  neuralgia,  chorea,  "neu- 
rasthenia," dyspepsia,  may  also  temporarily  disappear,  only  to  return 
when  the  environments  or  the  circumstances  of  the  patient  become 
slightly  less  favorable. 

The  patient  suffering  from  neurasthenia,  a  term  indefinitely  sig- 
nifying a  state  of  nervous  irregularity  or  exhaustion,  may  find  the 
pleasurable  experiences  of  travel  in  foreign  countries  highly  beneficial, 
and  the  aching  back,  the  painful  brow,  and  the  reduced  energy  may 
give  place  to  freedom  from  pain  and  greater  nervous  activity.  The 
same  patient,  returning  home  to  the  accustomed  duties  of  life,  brings 
back  the  same  physical  disadvantages  that  were  taken  abroad,  and 
soon  finds  that  these  disadvantages  produce  results  of  the  same  gen- 
eral class  as  those  suffered  before. 

It  is  not  always  that  the  nervous  symptoms  resulting  from  oculo- 
neural  disturbance  are  specifically  the  same  after  such  a  rest,  for  neu- 
roses are  changeable  by  reason  of  many  sorts  of  influence.  It  is  safe, 
however,  to  say  that  the  person  who  has  once  been  the  subject  of 
neurasthenia  in  any  of  its  forms  is  quite  likely  to  be  again  subject 
to  it  in  one  or  another  form  whenever  a  special  demand  upon  the 
energies  is  continued  for  a  considerable  time. 

Only  in  one  direction  can  the  sufferer  from  the  neuroses  from 
ocular  irregularities  look  for  permanent  and  complete  relief.  That 
direction  is  toward  the  radical  and  permanent  removal  of  the  cause 
of  the  disturbance. 

The  question  may  fairly  be  raised  whether  it  is  practicable  to 
remove  these  anomalous  conditions,  and  also  whether  the  risk  of 
creating  new  defects  is  not  so  great  as  to  render  the  undertaking 
undesirable,  even  admitting  that  under  the  most  favorable  circum- 
stances they  may  be  remedied. 


1  Archiv  fur  Ophthalmologie,  Bd.  8,  ii,  346. 


338  ANOMALIES  OF  MOTOR  MUSCLES. 

To  the  first  part  of  this  question  it  may  be  replied  in  the  most 
emphatic  manner  that  these  anomalous  relations  of  the  eye  muscles 
are  in  the  vast  majority  of  cases  removable.  To  the  second  part  of 
the  question  it  may  be  said  that  while  much  depends  upon  the  skill 
of  the  operator  and  his  judgment  in  respect  to  what  should  be  done, 
the  risk  of  inducing  new  anomalies  worse  than  the  first  is,  in  the 
hands  of  one  fully  qualified  to  treat  such  cases,  incomparable  to  the 
benefits  to  be  derived  from  a  proper  and  permanent  relief  from  the 
defects. 

Allowances  are  always  to  be  made  for  the  unavoidable  and  uni- 
versal imperfections  of  pioneer  work.  The  system  which  has  been 
presented  in  this  work  and  the  surgical  practice  based  upon  it  have 
been  recognized  during  a  comparatively  few  years,  and  it  is  true  that, 
failing  to  recognize  some  of  the  basic  conditions  which  have  been 
revealed  by  more  recent  research,  the  earlier  results,  however  satis- 
factory, on  the  whole,  were  far  less  certain  and  much  less  radical 
than  may  now  be  obtained  when  advantage  may  be  taken  of  these 
later  observations. 

The  success  of  later  efforts  to  correct  these  anomalies  has  ad- 
vanced proportionately  to  the  advance  in  knowledge  of  the  essential 
nature  of  the'  defects.  It  may  now  be  said  that  with  the  knowledge 
at  present  possessed  of  the  principles  and  phenomena  of  heterophoria 
and  the  kindred  conditions,  given  the  requisite  skill,  judgment,  and 
experience,  the  risks  of  surgical  treatment  for  these  defects  is  posi- 
tively insignificant. 

The  question  whether  a  patient  is  to  be  subjected  year  after  year 
to  the  disadvantages  of  a  defect  which  is  removable  because  it  may 
be  thought  more  safe  to  trust  to  temporary  means  of  .relief  is  one 
involving  more  than  the  momentary  suspension  of  symptoms. 

In  early  years  the  course  for  the  future  of  the  individual  is  often 
greatly  modified  by  the  presence  of  some  physical  feature  which  may 
act  as  a  handicap  in  the  race  of  life. 

The  great  principle  which  should  guide  in  all  the  surgical  treat- 
ment of  the  muscles  of  the  eyes  is  that  all  the  functions  of  movement 
should  be  made  more  perfect  and  more  harmonious  after  the  treat- 
ment than  before.  Such  a  principle  is  absolutely  antagonistic  to  the 
empyrical  practice  of  severing  a  muscle  with  its  accessories  from  the 
eyeball,  permitting  its  tendon  to  fall  back  within  its  sheath,  disquali- 
fying it  for  its  rotary  function,  for  the  purpose  of  a  cosmetic  im- 
provement or  the  neutralization  of  a  supposed  "insufficiency"  by  the 


SURGICAL  TREATMENT.  339 

creation  of  another  insufficiency.  Still  more  is  it  opposed  to  the 
infinitely  more  rude  practice,  at  present  somewhat  in  vogue,  of  tuck- 
ing the  tendon,  capsule  and  other  tissues  into  a  knot.  Such  an  opera- 
tion must  of  necessity  remain  an  enduring  blemish  and  as  surely 
induces  a  permanent  impediment  to  the  proper  motility  of  the  eye 
as  it  accomplishes  its  illy  considered  purpose.  A  tendon  which  has 
been  drawn  back  into  the  capsule  or  orbital  tissue  and  disabled  may 
sometimes,  by  good  fortune,  be  found  and  replaced,  restoring  passable 
motility;  but  a  tendon  which  has  been  folded  and  cicatrized  is  hope- 
lessly disabled. 

The  correction  of  heterophoria  does  not  demand  a  disabling  of 
an}T  muscle  for  the  relief  of  another  muscle.  The  purpose  of  the 
surgical  treatment  is  to  render  all  the  muscular  actions  as  nearly 
as  possible  normal,  meaning  by  normal  in  this  connection  the  best 
that  is  found  in  the  most  perfect  cases. 

To  arrive  at  such  a  desirable  end,  it  is  necessary  to  consider  all 
the  elements  in  any  given  case.  If  the  case,  for  example,  is  one  of 
csophoria,  it  does  not  follow  that  the  inner  muscles  are  too  tense  nor 
that  the  outer  muscles  are  relaxed.  The  cause  of  the  esophoria  may 
lie  in  the  fact  that  the  optic  axes  are  normally  directed  above  the 
plane  of  the  horizon  or,  much  more  frequently,  in  the  fact  that  there 
are  such  declinations  as  to  make  a  nervous  impulse  toward  conver- 
gence a  part  of  the  adjustment  for  parallelism  of  the  vertical  me- 
ridians. Esophoria  and  exophoria  are  rarely  primary  conditions. 

These  and  other  important  considerations  are  to  be  carefully 
weighed  in  every  instance  and  the  treatment  directed,  not  necessarily 
nor  generally  immediately  against  the  most  conspicuous  heterophoric 
tendency,  but  against  the  inducing  conditions  from  which  the  con- 
spicuous tendency  arises. 

Eye  muscle  tendons  should  never  be  cut-  off  and  allowed  to  fall 
back  in  operations  for  tenotomy.  Their  insertions  may  be  so  modi- 
fied as  to  produce  important  changes  in  the  relations  of  the  eyes 
while  remaining  largely  in  their  original  position.  The  slight  change 
of  direction  in  the  insertion  of  a  tendon  necessary  to  change  the 
position  of  the  vertical  meridian  from  an  important  declination  to 
an  actual  verticality  does  not  or  should  not  limit  its  rotating  func- 
tion, but  often  increases  it. 

Instead  then  of  proceeding  to  an  immediate  discussion  of  the 
surgical  means  for  the  direct  correction  of  the  different  forms  of 


340  ANOMALIES  OF  MOTOR  MUSCLES. 

heterophoria,   it   is   better  to   consider  the  means   of   correcting  the 
conditions  which  are  most  liable  to  induce  them. 

Of  these,  by  far  the  most  influential,  as  has  been  repeatedly  said 
already,  are  declinations.  We  may  therefore  first  study  methods  for 
the  correction  of  declinations. 


OPERATIVE  TEEATMENT  OF  DECLINATIONS. 

While  the  effects  of  declinations  may,  under  certain  circum- 
stances, be  modified  by  glasses,  spherical,  cylindrical,  or  prismatic, 
and  while  such  tonic  measures  as  have  already  (p.  327)  been  sug- 
gested may  be  of  temporary  use,  practically,  the  correction  can  only 
be  effected  by  surgical  interference. 

There  can  be  no  absolutely  direct  method  of  reaching  these 
anomalies  of  declination,  a  modification  of  the  tension  of  the  obliques 
being  the  only  exception,  and  it  would  be  a  bold  and  probably  a  most 
imprudent  surgeon  who  should  undertake  to  change  the  actions  of 
these  muscles. 

There  is  left,  then,  only  such  indirect  influence  upon  the  posi- 
tion of  the  eyeball  as  can  be  brought  about  by  changing  the  direction 
of  the  action  of  the  recti  muscles. 

If,  with  declination,  there  coexists  the  condition  of  anophoria 
or  of  katophoria,  somewhat  important  modifications  of  the  declina- 
tions may  be  accomplished,  while  at  the  same  time  the  plane  of  vision 
is  depressed  or  raised.  To  these  contingencies  we  shall  return.  At 
present  only  the  direct  operations  for  declination  are  to  be  considered. 

With  the  view  of  'preserving,  as  nearly  as  possible,  the  full  and 
equal  rotation  action  of  the  lateral  muscles  and  at  the  same  time 
avoiding  any  raising  or  lowering  of  the  direction  of  the  visual  line 
of  either  eye,  I  have  resorted  to  several  methods  of  procedure,  each 
progressively  more  effective  than  the  other,  until  at  present  only  one 
of  these  methods  is  employed,  except  in  cases  such  as  will  later  be 
described.  Although  the  earlier  methods  have  been  superseded,  it 
will  be  well  to  pass  in  review  the  process  of  evolution  to  the  more 
effective  operation  for  declination. 

Earlier  Operations. — The  first  of  these  was  the  operation,  a 
description  of  which  I  published  several  years  since  and  called  peri- 
tenotomy.  It  consisted,  essentially,  in  relaxing  a  part  of  the  insertion 
of  opposing  muscles  at  diagonally  opposite  points.  Thus,  if  the 
lateral  muscles  were  selected  for  operation  for  positive  (  +  )  declina- 


EXTENDO-CONTRACTION.  341 

tion,  the  upper  half  of  the  extcrnus  insertion  and  the  lower  half  of 
the  insertion  of  the  interims  were  relaxed.  By  this  means  about  1° 
or  possibly  2°  declination  could  be  corrected,  but  the  change  of 
direction  of  the  meridian  of  more  than  iy2°  required  an  extent  of 
relaxation  of  the  tendon  insertion  which  threatened  impairment  of 
the  action  of  the  muscles.  Practically,  then,  a  correction  of  1°  or  a 
little  more  was  all  that  could  be  hoped  for  with  a  conservative  opera- 
tion. This  gain  was  reached  by  some  sacrifice,  even  if  small,  of  the 
normal  tensions  of  the  muscles,  and  the  operation  was  soon  aban- 
doned. 

The  second  step  in  the  evolution  was  the  operation  which  I  called 
circumtraction  (vertical  or  lateral).  In  this  procedure  a  part  of  the 
insertion  of  opposing  muscles  was  separated  from  the  sclera,  and  this 
separated  part  was  carried  forward  into  a  previously  prepared  pocket, 
thus  advancing,  for  example,  the  upper  half  or  two-thirds  of  the 
insertion  of  the  internus  and  the  lower  half  or  two-thirds  of  the 
insertion  of  the  externus.  By  this  method  a  correction  of  a  larger 
degree  of  declination  could  be  effected,  but  here  again  there  was- 
danger  of  inducing  a  disproportionate  action  among  the  various 
muscles. 

The  third  step  in  the  evolution  of  an  operation  for  directly 
affecting  declination  is  what  I  have  termed  extendo-contraction.  It 
is  the  operation  which  I  find  the  most  practical  and  efficient  of  all 
the  methods  which  have  suggested  themelves. 

Extendo-contraction. — By  this  operation  the  full  rotation  action 
of  the  muscle  is  preserved,  no  heterophoria  is  induced,  eyes  which 
were  parallel  before  the  operation  remaining  so  after  it,  while  by  its 
means  a  greater  degree  of  correction  of  the  leaning  of  the  meridians 
can  be  brought  about  than  by  either  of  the  preceding  measures.  Even 
by  this  process  a  change  of  the  direction  of  the  meridians  of  2°  or  3° 
must  be  considered  a  favorable  result,  although  occasionally  a  much 
more  important  change  is  effected  by  a  single  operation. 

In  cases  of  high  degree  of  declination  the  operation  may  be  done 
on  one  muscle  at  one  time  and  on  another  at  another  time.  The 
selected  muscles  are  the  internus,  the  superior,  and  less  desirably  the 
externus. 

Of  course  it  may  be  done  on  the  inferior,  but  it  has  been  found 
prudent  to  avoid  operations  on  this  muscle  as  far  as  possible.  As 
the  declination  operation  is  not  an  easy  or  simple  process,  I  shall 
describe  it  in  detail,  premising  that  it  is  of  the  highest  importance 


342  ANOMALIES  OF  MOTOR  MUSCLES. 

that  the  various  steps  should  be  taken  exactly  in  the  order  and  in  the 
manner  described.  Let  it  be  assumed  that  the  internal  rectus  of  the 
left  eye  has  been  selected  for  the  operation  on  account  of  a  -f-  declina- 
tion -i°.  The  surgeon,  standing  on  the  right-hand  side  of  the  patient, 
the  lids  being  separated  by  a  speculum,  the  patient  is  told  to  direct 
the  eyes  to  the  left  and  down.  Then  the  surgeon,  seizing  a  very  small 
fold  of  the  conjunctiva  (i/>  millimeter)  by  the  fine  forceps  (Fig.  135), 
makes  an  opening  with  the  fine-pointed  scissors  (Fig.  136)  just  over 
the  upper  border  of  the  insertion  of  the  muscle,  and,  pushing  the 
blades  of  the  scissors  forward  while  avoiding,  so  far  as  possible,  en- 
largement of  the  small  opening  in  the  conjunctiva,  he  forms  a  pocket 
nearly  up  to  the  border  of  the  cornea  and  extending  more  than  half- 
way down  the  length  of  the  tendon  insertion.  (By  skillful  manipu- 
lation the  very  small  opening  in  the  conjunctiva  may,  by  the  elasticity 


Fig.  132. — Diagram  Illustrating  the  Change  of  the  Line  of  Insertion 
of  the  Tendon  of  the  Internus. 

of  the  tissue,  escape  any  enlargement,  so  that  at  the  close  of  the 
operation  it  returns  to  its  original  small  extent  of  %  a  millimeter.) 
The  pocket  being  made,  the  operator  next  passes  to  the  left  side 
of  the  patient.  He  now  seizes  the  insertion  of  the  tendon  at  its  upper 
part  in  the  fine  blades  of  the  forceps  and  separates  it  to  the  extent 
of  a  few  millimeters  only,  working  carefully  under  the  conjunctiva, 
observing  care  not  to  enlarge  the  small  conjunctival  opening,  which 
will  stretch  without  tearing.  He  then  introduces  the  deliqate  sharp 
hook  (Fig.  137)  between  this  separated  part  and  the  sclera  and  when 
it  has  been  carried  back  to  the  desired  extent,  presses  the  sharp  point 
against  the  inner  surface  of  the  tendon  and  draws  it  forward.  The 
hook  should  engage  itself  sufficiently  below  the  border  of  the  tendon 


INSTRUMENTS. 


343 


Fig.  133. — Flexible  Eye  Speculum. 


Fig.134.— Lid  Retractor. 


Fig.  136.— Scissors. 


Fig.  137. — Fine,  Sharp  Hook. 


Fig.  138.— Small  Tendon  Hook. 


Fig.  140.— Needle-holder. 


Fig.  142.— Catch  Forceps. 

J)B.  STEVENS'S  INSTRUMENTS  FOB  OPERATIONS  ON  THE  EYE  MUSCLES. 


344  ANOMALIES  OF  MOTOR  MUSCLES. 

and  sufficiently  back  to  insure  the  drawing  forward  of  that  part  of 
the  tendon.  The  part  of  the  tendon  engaged  by  the  hook  is  now 
forced  through  the  little  opening  in  the  conjunctiva,  when  a  small 
curved  needle,  one  of  two  attached  to  a  very  fine  thread,  is  carried 
twice  througli  the  protruding  portion  of  the  tendon,  which  is  then 
allowed  to  retreat  within  the  conjunctiva.  An  assistant  takes  the  two 
needles,  holding  the  thread  out  of  the  way  of  the  operator,  who  now, 
using  the  small  tenotomy  hook  (Fig.  138),  dissects  from  the  sclera  the 
remainder  of  the  insertion  still  with  care  not  to  enlarge  the  original 
conjunctival  wound.  If  the  tendon  is  unusually  broad,  a  counter- 
opening  near  the  lower  border  of  the  tendon  is  made,  and  the  division 
of  the  tendon  is  completed  from  this  point.  The  extent  of  the  di- 
vision may  be  ascertained  by  the  phorometer  before  the  next  step  is 
entered  upon.  If  10°  or  12°  exophoria  has  been  induced  the  lower 
border  of  the  tendon  is  free. 

(One  who  has  done  the  operation  many  times  will  be  able  to 
judge  of  the  sufficiency  of  the  division  of  the  insertion  without  the 
use  of  the  phorometer.) 

The  assistant  now  inserts  a  director  through  the  conjunctival 
wound  into  the  pocket,  carrying  it  somewhat  above  the  border  of  the 
cornea.  One  needle  is  carried  in  the  direction  of  the  probe,  making 
its  exit  above  and  near  the  border  of  the  cornea.  The  second  needle 
is  then  carried  through,  3  or  4  millimeters  below,  and  the  thread  is 
drawn  and  tied  in  a  slip-knot.  An  esophoria  of  about  7°  to  9°  should 
be  induced.  If  more  than  this  has  been  brought  about,  the  thread 
must  be  loosened  until  the  amount  does  not  exceed  the  desired  extent. 
Then  the  knot  is  made  fast  and  the  thread  is  cut.  The  thread  should 
be  extremely  fine,  of  silk.  Xo  catgut  is  sufficiently  deHcate  for  this 
operation. 

On  the  following  day  there  should  be  neither  esophoria  nor  exo- 
phoria (assuming  that  there  was  none  before),  and  there  will,  if  the 
operation  has  been  skillfully  done,  be  no  apparent  wound  of  the 
conjunctiva,  though  there  will,  of  course,  be  redness  and  some  slight 
thickening. 

By  referring  to  the  diagram  (Fig.  132)  an  idea  may  be  acquired' 
of  what  is  to  be  accomplished  by  the  operation.  The  equator  of  the 
eyeball  is  indicated  by  a,  and  the  tendon  of  the  internal  rectus  by  &. 
The  solid  line  represents  the  direction  of  the  insertion  of  the  tendon 
before  the  operation,  while  the  dotted  line  represents  the  position  of 
the  insertion  afterward. 


PROCEDURE  IN  ANOPHORIA  AND  KATOPHORIA.  345 

It  will  be  seen  that  the  extremity  of  the  tendon  at  c  has  been 
advanced  toward  the  cornea,  while  the  lower  extremity  has  fallen 
somewhat  back,  giving  the  insertion  an  oblique  direction.  The  result 
of  this  oblique  direction  should  be  to  influence  the  vertical  meridian 
to  lean  from  the  left  farther  toward  the  right. 

In  order  to  insure  a  proper  amount  of  pulling  back  of  the  lower 
half  of  the  tendon  and  no  more,  and  to  maintain  the  fan-like  expan- 
sion of  the  insertion,  it  is  best  before  finally  releasing  the  lower  half 
of  the  insertion  to  insert,  through  a  minute  conjunctival  opening,  a 
second  suture  at  the  lower  border  of  the  tendon,  and,  drawing  only 
sufficiently  to  hold  the  expanse  in  position,  avoid  a  too  narrow  inser- 
tion. 

By  means  of  this  operation,  even  with  no  contraction  or  relaxa- 
tion of  the  tendon,  a  preexisting  exophoria  or  esophoria  may  be  found 
to  disappear. 

PROCEDURE  ix  AXOPHORIA  AXD  KATOPHORIA. 

A  careful  consideration  of  the  principles  of  torsions,  as  shown 
in  Section  XIV,  will  show  that  if  the  normal  direction  of  the  visual 
plane  is  at  an  angle  above  the  horizon  when  the  head  is  in  the  primary 
position,  there  must  result  a  certain  extent  of  torsion  in  depressing 
the  plane  of  regard  to  the  horizon  when  convergence  occurs.  The 
irregular  torsion  increases  as  the  plane  of  regard  is  depressed  with 
convergence.  In  case  of  normal  declinations,  then,  these  torsions  may 
add  materially  to  the  native  anomaly  or  they  may  neutralize  it. 

As  a  matter  of  experience  it  is  found  that  with  very  high  rota- 
tions of  the  eyes,  whether  associated  or  not  with  restricted  rotations 
downward,  the  normal  declinations  are,  as  a  rule,  marked  features 
of  the  ocular  adjustments.  It  will  be  seen  then  that  anophoria  is  not 
only  liable  to  be  complicated  by  important  declinations,  but  that  the 
resulting  torsions  may  increase  the  effect  of  these  declinations  in 
most  of  the  ordinary  adjustments  of  the  eyes. 

Were  it  desirable  that  the  anophoric  condition  should  be  modi- 
fied directly  by  a  reduction  of  the  upward  rotations,  the  operation 
might  be  that  for  graduated  tenotomy  of  each  superior  rectus,  as 
described  below.  But  since  a  high  grade  of  anophoria  is  nearly  al- 
ways accompanied  by  important  declinations,  the  correction  of  the 
defect  should  not  generally  be  attempted  in  this  simple  manner. 

Should  the  operation  have  for  its  objective  purpose,  not  only  a 


346  ANOMALIES  OF  MOTOR  MUSCLES. 

depression  of  the  visual  plane,  but  a  correction  of  declination,  the 
procedure  must  be  modified  accordingly. 

Should  it  be  required,  for  example.,  to  reduce  the  plane  of  vision 
5°  and  to  correct  a  +  declination  of  the  right  eye,  and  a  negative 
declination  of  the  left,  the  most  simple,  but  not  necessarily  the  most 
effectual,  way  would  be  to  dissect  the  insertion  of  the  superior  rectus 
of  the  right  from  the  medial  toward  the  temporal  border,  leaving  so 
much  of  the  temporal  border  as  may  be  required  to  graduate  the 
depression  of  the  plane  of  vision,  while  for  the  left  eye  the  dissec- 
tion of  the  insertion  of  the  superior  rectus  would  proceed  from  the 
temporal  toward  the  medial  side,  leaving  the  graduating  band  at  the 
medial  border. 

This  was  my  earlier  method  of  procedure  in  these  cases,  but 
experience  soon  showed  that  it  is  better  even  in  these  cases  to  do 
the  operation  for  cxtendo-contraction,  but  permitting  of  a  slight  set- 
ting back  of  the  superior  rectus.  This  is  best  accomplished  by  two 
sutures,  as  described  above,  thus  controlling  the  situation  and  direc- 
tion of  the  new  insertion. 

It  is,  even  in  cases  of  the  remarkably  high  rotations  sometimes 
found  in  converging  strabismus,  not  safe  to  carry  the  effects  of  a 
tenotomy  of  the  superior  rectus  more  than  4°  or  5°  prism,  since 
beyond  that  point  the  restraining  fibers  at  the  borders  of  the  inser- 
tions are  severed,  and  in  the  subsequent  acts  of  adjustment  of  the 
eyes  irregular  torsions  are  almost  sure  to  result.  Hence,  it  is  always 
in  these  extreme  cases  necessary  to  control  the  form  and  obliquity  of 
the  new  insertion. 

For  the  correction  of  katophoria  the  graduated  tenotomy  is  even 
less  advisable.  Indeed,  operations  on  the  inferior  recti  are  to  be 
strictly  avoided.  There  may  arise  contingencies  in  which  it  may 
become  necessan"  to  interfere  with  the  normal  insertions  of  the  infe- 
rior rectus,  but  in  such  case  the  two  extreme  borders  of  the  insertion 
should  be  secured  (as  in  the  operation  for  extendo-contraction)  and 
replaced  in  such  a  manner  as  to  give  the  full  expanse  to  the  insertion, 
which  should  not  be  transferred  so  much  in  the  lateral  direction  as 
to  induce  torsion  in  the  act  of  depressing  the  plane  of  regard. 

As  this  demands  extreme  caution,  and  may,  even  when  great 
skill  is  exercised,  prove  unfortunate,  it  is  a  s^fe  rule  generally  to 
refrain  from  any  interference  with  this  tendon. 

To  increase,  then,  the  elevating  action  of  the  superior  recti,  con- 
traction may  be  done  so  as  to  augment  their  upward  pull. 


OPERATIVE  TREATMENT  FOR  HETEROPHORIA.  347 

The  operation  for  tendon  contraction  is  accomplished  according 
to  the  method  described  in  another  part  of  this  section.  As  in  the 
case  of  anophoria  it  may  be,  and  generally  is,  required  to  vary  the 
procedure  with  reference  to  an  existing  declination.  With  this  in 
view,  with  a  -}-  declination  the  main  suture  will  be  inserted  to  the 
temporal  side  of  the  center  of  the  tendon,  the  graduating  suture  at 
the  nasal  side.  With  negative  declination  the  main  suture  would  be 
carried  to  the  nasal  side. 

OPERATIVE  TREATMENT  FOR  HETEROPHORIA. 

The  truth  which  should  be  uppermost  in  the  mind  of  every  one 
who  undertakes  an  operation  for  the  correction  of  heterophoria  is 
that  every  disability  of  the  rotating  function  of  a  muscle  is  to  be 
avoided,  and  that  the  purpose  of  surgical  treatment  is  to  enable  the 
eyes  to  move  with  greater,  not  with  less  freedom,  and  not  irregularly. 
The  object  of  operations  for  heterophoria  should  be  to  establish 
exactly  equal  and  favorable  movements  of  the  eyes,  and  there  is  no 
justification,  under  any  circumstances,  for  disabling  any  one  muscle. 
Especially  is  there  never  an  excuse  for  disabling  one  muscle  because 
its  opponent  is  disabled. 

Although  it  might  be  possible,  for  example,  to  bring  the  images 
in  line  in  a  case  of  exophoria  by  an  extensive  relaxation  of  one  ex- 
ternal rectus  while  the  other  remained  intact,  the  unequal  rotations 
thus  induced  would  be  a  permanent  source  of  evil. 

Again,  since  the  conditions  of  heterophoria  are  very  frequently 
the  results  of  declinations  or  of  unfavorable  plane  of  vision,  opera- 
tions for  heterophoria  should  remain  secondary  to  these  original 
conditions.  If,  for  example,  correcting  a  positive  declination  for 
each  eye  the  previously  existing  exophoria  will  disappear,  it  is  surely 
more  philosophic  to  attend  to  the  declinations  first.  In  the  same  way 
a  suitable  correction  of  anotropria  may  remove  an  esophoric  tendency. 
As  a  matter  of  practice  during  the  past  few  years  I  find  it  very  rarely 
necessary  to  operate  directly  for  heterophoria.  A  large  majority  of  all 
operations  having  these  conditions  in  view  are  such  as  are  primarily 
directed  against  declinations,  katophoria,  or  anophoria.  The  direct 
operations  for  heterophoria  are  graduated  tenotomies  and  tendon  con- 
tractions. They  are  the  operations  which  were  described  by  myself 
many  years  ago.1 


'"Prize    Essay,"   Royal   Acad.   Med.,    Belgium,    1883. 


348  ANOMALIES  OF  MOTOR  MUSCLES. 

It  is  true  that  graduated  tenotomies  have  been  most  successful  in 
bringing  pronounced  relief  in  great  numbers  of  cases,  and  it  is  safe 
to  say  that  the  results  have  been  on  the  whole  eminently  serviceable. 
Some  disadvantages  must,  however,  be  conceded.  Even  in  the  hands 
of  the  most  skillful  it  is  not  always  possible  to  determine  the  exact 
point  beyond  which  a  relaxation  cannot  be  safely  carried.  The  result, 
although  in  experienced  hands  rare.,  is  an  occasional  overcorrection 
which  becomes  most  annoying.  Again,  even  with  much  care,  the  rota- 
tions of  the  two  eyes  are  not  always  preserved  equal,  and,  of  more  con- 
sequence than  all,  by  even  a  millimeter  of  relaxation  of  a  rectus  muscle 
the  normal  tension  of  the  muscles  which  hold  the  eyes  in  place  is  some- 
what modified. 

For  these  reasons,  since  an  even  more  effective  method  and  one 
not  subject  to  either  of  the  disadvantages  mentioned  has  been  found  in 
the  operation  for  extendo-contraction,  it  is  better  to  choose  the  pro- 
cedure which,  though  somewhat  more  complicated  and  requiring 
greater  skill,  offers  the  greater  advantages. 

Bearing  this  in  mind,  a  minutely  detailed  description  of  the  op- 
eration for  graduated  tenotomy  will  still  be  in  place.  There  are  oc- 
casions when  it  is  the  only  advisable  mode  of  procedure. 

GRADUATED  TENOTOMY. 

The  description  of  an  operation  for  graduated  tenotomy  for 
heterophoria  of  either  of  the  recti  muscles  will  serve  sufficiently  well 
for  all.  We  may  therefore  suppose  that  a  graduated  tenotomy  is  to- 
be  done  for  the  internal  rectus  of  the  right  eye. 

The  speculum  being  in  place,  the  patient  directs  both  eyes  well 
to  the  right.  The  surgeon  takes  with  his  fine  forceps  (Fig.  135)  a 
minute  fold  of  conjunctiva  at  the  center  of  the  insertion  of  the  ten- 
don. Drawing  the  little  fold  of  conjunctiva  slightly  away  from  the 
eyeball,  with  the  extreme  points  of  his  tenotomy  scissors  (Fig.  136) 
he  snips  the  fold  transversely  so  that  an  opening  about  half  a  milli- 
meter in  extent  is  made  through  the  membrane.  Xow  the  forceps, 
the  points  being  closed,  are  pressed  into  the  little  opening  and  slightly 
backward,  when  the  points  are  permitted  to  spring  apart,  after  which 
they  are  again  closed,  this  time  holding  a  small  fold  of  the  tendon 
just  behind  the  insertion.  This  little  fold  of  tendon  being  put  on  the 
stretch,  the  fine-pointed  scissors,  by  little  snips,  dissect  the  tendon 
from  the  eyeball  between  the  layers  of  the  capsule  (which  should 
remain  intact)  toward  one  border  of  the  insertion.  The  sense  of  feel- 


GRADUATED  TENOTOMY.  349 

ing  of  the  fingers  against  the  rings  of  the  scissors  will,  in  the  hands 
of  one  skilled  in  the  operation,  inform  him  of  his  approach  to  the 
border  and  warn  him  against  its  destruction. 

The  dissection  and  the  knowledge  of  the  distance  to  which  it 
should  be  carried  will  often  be  facilitated  by  introducing  the  slender 
blunt  hook  (Fig.  138),  by  the  feeling  of  which  the  amount  of  tension 
remaining  as  the  dissection  approaches  the  border  of  the  tendon  can 
be  estimated  and  the  extent  of  the  border  to  remain  can  be  graduated. 
(In  extreme  cases,  like  strabismus,  the  surgeon  may  determine  to 
continue  the  dissection  to  the  extreme  border,  but  that  should  never 
be  divided,  and  as  far  as  possible  both  the  anterior  and  posterior  lay- 
ers of  the  capsule  must  be  preserved.  In  fact,  there  should  be  such 
connections,  both  along  the  course  of  the  dissected  part  of  the  inser- 
tion and  at  the  borders,  that  there  can  be  no  doubt  that  the  muscle 
will  be  held  in  its  proper  relation  to  the  eye.  Such  an  extreme  meas- 


Fig.  143. — Stevens's  Operation  for  Tenotomy.    c,  The  cornea,    m,  The 
muscle.    1 1',  The  tendon  at  its  insertion. 

ure  as  permitting  the  tendon  to  withdraw  into  the  sheath  will  never 
be  required,  even  in  strabismus. 

Having  made  the  dissection  toward  one  border  the  scissors  are 
turned  toward  the  other  and  this  portion  of  the  insertion  is  dis- 
sected'with  equal  care. 

The  diagram  (Fig.  143)  shows  the  position  and  extent  of  the 
dissection. 

The  black  outline  of  muscle  and  tendon  represents  the  original 
form  and  position.  The  larger  red  dot  indicates  the  position  and  size 
of  the  conjunctival  opening. 

The  dotted  red  line  just  behind  the  insertion  represents  the  posi- 
tion and  approximate  extent  of  the  dissection  of  the  tendon.  The 
solid  curved  red  line  behind  this  is  the  new  position  taken  by  the 
insertion  after  the  operation,  which  is  permitted,  less  by  the  exten- 


350  ANOMALIES  OF  MOTOR  MUSCLES. 

sion  of  the  uncut  fibers  at  the  borders  than  by  the  change  in  the  form 
of  the  tendinous  end  of  the  muscle  as  shown  by  the  dotted  lines  at 
the  sides. 

The  dot  at  the  center  of  the  line  of  dissection  is  the  position  of 
and  the  relative  size  of  the  opening  through  the  conjunctiva. 

[The  dotted  line  at  a  (Fig.  144)  shows  the  extent  and  position 
of  the  conjunctival  opening  in  the  von  Graefe  operation.  The  red 
line  at  b  the  section  of  the  tendon,  extending  beyond  the  border  to 
include  the  capsule,  d  indicates  the  position  taken  after  a  moderate 
"setting  back"  (!%").  The  settings  back  are,  according  to  von 
Graefe,  as  much  as  3",  which  would  carry  the  line  d  back  to  d'.  In 
extreme  cases  he  sets  the  tendon  back  from  4"  to  6",  which  would  be 
well  toward  in. 

Whether  the  insertion  is  set  back  to  d  or  to  d'  it  is  drawn  into  the 


Fig.  144.- — Diagramatic  Representation  of  von  Oraefe's  Operation  for 
Tenotomy.  Scale,  3X1.  c,  The  cornea.  111,  The  muscle,  t,  t,  The  tendon 
at  its  insertion. 

folds  of  the  capsule  and  becomes  contracted  in  breadth  and,  of  course, 
separated  from  the  surface  of  the  sclera. 

Except  for  the  line  of  division  of  the  conjunctiva,  this  dia- 
gram will  serve  for  the  operations  of  Critchett,  Lebreich,  and  others 
more  recently  suggested.] 

With  as  little  delay  as  possible  the  patient  is  to  be  placed  in  the 
examination  chair  where  the  tests  by  the  phorometer  and  by  prism-? 
by  abduction  are  to  be  made. 

It  is  safe  in  moderate  cases  to  carry  the  correction  to  1°  of 
exophoria,  if  the  operation  is  for  esophoria,  and  the  abduction  to  10°, 
for  at  the  moment  of  the  operation  there  is  likely  to  be  a  greater  ab- 
duction than  will  be  found  half  an  hour  later,  and  with  this  record 
by  the  phorometer  and  prism  it  may  be  expected  that  within  the  next 


GRADUATED  TENOTOMY.  351 

twenty-four  hours  there  will  he  still  slight  esophoria  and  a  somewhat 
restricted  abduction,  conditions  permitting  the  completion  of  the 
change  in  the  relations  of  the  visual  lines  by  an  operation  of  the 
same  kind  and  as  nearly  as  possible  of  the  same  extent  on  the  op- 
posite internus. 

If  the  operation  is  on  the  externus  for  exophoria  the  record  of 
the  phorometer  should  be  0°,  but  the  abduction  may  be  reduced  to 
5°  at  the  moment  of  the  operation.  In  either  case  the  conditions  of 
abduction  and  of  rotation  are  to  be  considered.  If  in  the  case  of  eso- 
phoria the  abduction  was,  before  the  operation,  greater  in  proportion 
to  the  standard  of  8°  than  it  should  have  been  to  correspond  with  the 
degree  of  esophoria,  the  abduction  immediately  after  the  operation 
may  be  very  little  above  10°  ;  and  should  it  have  been  less  in  pro- 
portion, as,  for  example,  abduction  2°,  esophoria  3°,  it  will  be  prudent 
not  to  carry  the  immediate  effect  of  the  operation  to  an  abduction  as 
high  as  10°.  So,  also,  if  there  is  little  to  be  lost  in  rotation,  the 
greatest  care  is  to  be  observed  not  to  restrict  it  unnecessarily.  These 
exceptional  cases  should,  in  fact,  rarely  be  treated  for  simple  hetero- 
phoria,  as  they  belong  to  the  class  of  declinations. 

Should  the  surgeon  be  so  unfortunate  as  to  find  that  by  an  error 
of  judgment  he  has,  in  operating  for  esophoria,  gained  an  exophoria 
of  even  a  few  degrees  he  should  at  once  introduce,  at  the  exact  center 
of  the  free  end  of  the  tendon,1  a  very  delicate  suture,  carrying  it 
through  the  cut  edge  of  the  conjunctiva  at  the  corneal  side.  Occa- 
sionally, but  rarely,  there  is  an  exception  to  the  rule  that  the  over- 
correction  must  be  neutralized  at  once.  For  if  in  these  exceptional 
cases  the  patient  is  permitted  to  wait  an  hour  or  less,  the  exophoria 
and  the  excessive  abduction  may  disappear  and  the  rotation  may  be 
found  quite  sufficient.  The  suture  when  used  is  to  include  as  little 
as  possible  of  the  tissue  of  the  tendon  and  of  the  conjunctiva.  It 
is  to  be  drawn  with  care  until  the  exophoria  has  been  overcome,  as 
shown  by  the  phorometer;  then  the  knot  is  to  be  made  fast. 

This  procedure,  although  sometimes  demanded  in  the  practice  of 
the  most  skillful,  is  always  unfortunate. 

The  old  teaching,  that  after  an  operation  on  a  rectus  muscle 
a  restraining  suture  should  be  introduced  in  the  conjunctival  wound, 


1  In  all  these  details  it  is  assumed  that  the  operation  is  only  for  heter- 
ophoria,  not  for  declination  and  heterophoria.  Should  it  be  desired  to  do 
tenotomy  with  a  view  to  both  conditions  these  principles  are  to  be  borne  in 
mind,  but  modified  according  to  the  circumstances. 


352  ANOMALIES  OF  MOTOR  MUSCLES. 

originated  before  the  doctrine  of  heterophoria  was  known,,  and  when 
an  extensive  wound  of  the  conjunctiva  needed  to  be  united  in  order 
to  avoid  the  large  cicatrix.  Xo  such  procedure  is  now  required  and  no 
suture  even  as  delicately  introduced  as  has  been  directed  is  less  than 
a  misfortune. 

The  error  of  hoping  that  because  an  excess  of  correction,  espe- 
cially in  exophoria,  even  when  resulting  in  diplopia,  is  sometimes 
followed  by  single  vision  and  even  esophoria,  the  overcorrection  may 
correct  itself,  is  a  serious  one.  These  apparent  corrections  are  ac- 
companied by  disabled  rotation  on  the  part  of  the  eye  operated  on, 
and  if  the  wound  is  permitted  to  heal,  a  perfect  equilibrium  can  only 
with  much  difficulty  be  re-established. 

One  of  the  most  serious  errors  in  operations  for  heterophoria  is 
the  attempt  to  atone  for  an  overcorrection  of  one  muscle  by  an  opera- 
tion on  another. 

For  example,  if,  as  the  result  of  a  tenotomy  of  an  internus  of  one 
eye  an  exophoria  is  induced,  it  is  inexcusable  to  cut  the  externus  in 
order  to  relax  that  muscle  equally  with  the  excess  of  relaxation  of 
the  other. 

JYo  overcorrection  should  lie  corrected  by  a  new  tenotomy. 

TENDON  CONTRACTION. 

It  may  be  desirable  instead  of  doing  a  graduated  tenotomy,  thus 
relaxing  a  muscle,  to  contract  the  opponent.  Thus,  there  would  in 
most  cases  of  exophoria  result  a  less  degree  of  restriction  in  the 
lateral  rotations  were  we  to  contract  the  tendons  of  the  interni  rather 
than  relax  those  of  the  externi.  In  other  cases  both  granulated  ten- 
otomy and  contractions  may  be  desirable. 

The  operation  for  tendon  contraction  is  commenced  as  is  that 
for  graduated  tenotomy  by  making  a  transverse  slit  of  half  a  milli- 
meter in  extent  over  the  point  of  insertion  of  the  tendon.  (As  the 
operation  proceeds  this  slit  is  considerably  extended,  but  if  the  tissues 
are  not  torn  the  slit  will  return  to  its  original  size  after  a  few  hours.) 

Lifting  the  border  of  the  conjunctiva  nearest  the  cornea  by  the 
fine  forceps  (Fig.  135),  a  little  pocket  is  made  by  the  points  of 
the  scissors  or  by  the  lance  probe  (Fig.  141)  extending  under  the 
conjunctiva  more  or  less  toward  the  cornea  in  proportion  to  the 
greater  or  less  effect  which  it  is  proposed  to  induce.  The  pocket  hav- 
ing been  made,  the  forceps  seize  the  central  portion  of  the  tendon 
and  it  is  dissected  from  the  eyeball  as  in  the  operation  for  tenotomy. 


TENDON  CONTRACTION.  353 

By  means  of  the  scissors  or  by  that  of  the  lance  probe  the  tendon  is 
to  be  freed  from  any  attachment  to  the  surrounding  tissues,  espe- 
cially from  any  adhesions  to  the  sclera. 

The  fine  tendon  crotchet  (Fig.  137)  now  catches  it  at  the  center 
and  a  little  behind  the  section  and  draws  it  forward,  or,  if  the  hook 
proves  to  be  ineffectual  to  hold  it  during  the  next  stages  of  the  opera- 
tion, the  fine  fixation  forceps  with  catch  may  be  used.  (Fig.  142). 
The  tendon  is  drawn  forward  through  the  little  conjunctival  open- 
ing, when  one  of  the  needles  from  a  thread  of  silk  armed  at  each 
end  with  a  needle  is  passed  through  the  central  part  from  a  half  to 
a  full  millimeter  or  even  more  behind  the  cut  extremity  and  then 
turned  back,  thus  passing  twice  through  the  tendon.  Bringing  the 
needle  forward  until  the  two  extremities  of  this  thread  are  about 
equal  in  length,  an  assistant  carries  the  small  grooved  director  (Fig. 
1391)  into  the  pocket  already  made,  and  one  of  the  needles,  passing 
by  the  side  of  this  probe,  which  acts  as  a  guide,  is  made  to  penetrate 
the  conjunctiva  at  the  extreme  end  of  the  pocket  and  the  thread  is 
drawn  through.  The  other  needle  and  its  thread  are  managed  in 
like  manner,  the  second  needle  penetrating  a  little  to  one  side  of  the 
first  in  order  to  allow  between  the  two  threads  a  little  bridge  of  tissue. 
Now,  the  assistant  holding  the  conjunctiva  at  the  border  of  the  wound 
by  means  of  fine  forceps,  the  surgeon  draws  upon  the  ends  of  the 
thread,- forcing  the  cut  end  of  the  tendon  into  the  little  pocket,  and 
when  he  has  thus  advanced  it  to  his  satisfaction  he  fastens  the  threads 
by  tying  them  across  the  little  bridge. 

If  the  effect  to  be  produced  is  considerable,  two  sutures  may  be 
introduced,  one  at  each  border  of  the  tendon.  Two  small  openings 
in  the  conjunctiva  may  be  made,  but  by  skillful  manipulation,  the 
one  small  opening  at  the  center  may  serve  for  the  introduction  of 
both  sutures. 

No  dressing  or  cover  and  no  especial  care  is  required  beyond 
that  needed  for  perfect  cleanliness,  and  from  the  fourth  to  the  sixth 
day  the  suture  may  be  removed.  The  greatest  danger  in  these  cases 
arises  from  the  use  by  the  patient  of  a  soiled  handkerchief  with 
which  he  rubs  the  eye.  Against  this  danger  the  strictest  injunctions 
are  to  be  enforced. 


Devised  by  Dr.  Charles  W.  Stevens. 


354  ANOMALIES  OF  MOTOR  MUSCLES. 

SECTION  XLYII. 

Class  IV. 
HETEROTROPIA— STRABISMUS. 

Adjustments  of  ilic  Directing  llnscles  of  tlie  Eyes  in  Which  the 
Two  Visual  Lines  Are  so  Related  that  Binocular  Vision  is  Habit- 
ually Absent. 

Under  normal  conditions  when  an  eye  is  directed  to  a  given 
point,  the  point  of  fixation,  the  visual  line  connects  this  point  of 
fixation  and  the  macula,  passing  through  the  nodal  point. 

The  direction  of  the  visual  line  to  the  point  of  fixation  is  effected 
practically  through  the  influence  of  the  various  muscles  which  are 
connected  with  the  external  portion  of  the  eyeball.  Muscles  in  the 
vicinity  of  the  orbit  may  serve  in  some  measure  as  auxiliaries  to  these 
directing  muscles. 

Under  ordinary  circumstances  the  two  visual  lines  unite  at  the 
point  of  fixation,  when  binocular  vision  results. 

There  are  limits  to  the  field  of  ordinary  binocular  vision.  For 
example,  there  is  a  limit  to  the  ability  of  the  directing  muscles  to 
bring  both  visual  lines  to  a  point  of  fixation  very  near  to  the  eyes  or 
far  to  either  side  or  for  a  very  high  point. 

The  fact  that  normally  adjusted  eyes  cannot  fix  for  binocular 
vision  every  point  in  space  does  not  mean  that  such  eyes  are  not 
suited  to  binocular  vision.  But  there  is  a  varying  range  for  the  fixa- 
tion of  the  eyes  in  unison  for  different  persons. 

It  is  only  when,  under  normal  conditions,  there  is  an  inability 
to  thus  direct  the  two  eyes  so  that  within  the  ordinary  field  of  fixation 
the  visual  lines  are  not  so  directed  as  to  meet  at  the  point  of  regard 
that  the  relations  of  the  visual  lines  are  considered  as  anomalous. 

It  may  then  be  said  that  when,  within  this  ordinary  range  of 
fixation  and  under  normal  circumstances  the  visual  lines  of  the  two 
eyes  do  not  meet  at  the  given  fixed  point  there  is  a  condition  known 
as  strabismus. 

The  word  strabismus  is  derived  from  the  Greek  word  <r7y>a/?6s/u.os, 
a  squinting.  Other  terms  used  to  express  the  deviation  of  the  eyes 
explain  themselves.  They  are,  lucitas  (Lat.),  squint;  vue  louche 
(Fr.),  distorio  oculorum,  visus  obliquus,  yeux  a  travers,  Scheil,  etc. 


HETEROTROPIA.  355 

In  order  to  differentiate  the  strabismus  which  occurs  with  the 
normal  rotations  of  the  eyes  from  the  forms  which  occur  when  the 
motile  apparatus  is  disabled,  it  is  customary  to  apply  to  the  first 
class  of  cases  the  term  '"concomitant,"  and  to  the  other  "paralytic." 

The  term  heterotropia  is  used  as  a  part  of  a  systematic  classi- 
fication. Inasmuch  as  the  generally  received  idea  of  strabismus  is  that 
of  the  apparent  turning  of  one  eye  away  from  the  direction  of  its 
fellow,  it  is  desirable  to  associate  the  idea  of  such  a  failure  of  the 
visual  lines  to  cross  at  the  point  of  fixation,  even  although  no  devia- 
tion is  conspicuous  to  another  person,  with  some  term  intended  from 
the  beginning  to  indicate  such  a  deviation  as  will  induce  double 
vision,  conscious  or  unconscious,  independently  of  the  appearance  of 
the  eyes. 

The  question  of  the  appearance  of  turning  of  the  eyes  has  in 
the  literature  of  the  subject  been  so  prominently  brought  to  the 
attention  that  it  is  not  easy  to  divest  the  mind  of  the  idea  that  with 
strabismus  a  noticeable  turning  of  one  eye  is  essential  to  the  condi- 
tion. Thus,  Bonders,  in  his  discussions  of  strabismus,1  gives  many 
pages  to  the  appearances  which  may  be  mistaken  for  strabismus.  The 
^extent  of  the  angle  a  and  the  liability  to  mistake  it  for  a  diverging  or 
•converging  strabismus  occupies  a  very  large  space  in  the  discussion. 

As  such  slight  appearances  should  not  be  reckoned  as  essential 
elements  in  the  investigation  of  squinting  and  as  the  determination 
of  the  existence,  kind,  and  degree  of  strabismus  should  be  questions 
of  a  purely  optical  character,  it  is  well,  even  beyond  the  necessity  of 
suitable  terms  for  classification  of  muscular  anomalies,  to  employ  a 
term  to  which  false  notions  of  the  character  of  the  condition  dis- 
cussed are  not  associated.  Heterotropia  is  the  term  therefore  here 
employed,  not  only  a  convenient  term  for  classification,  but  a  useful 
substitute  for  a  word  to  which  too  vague  meanings  are  attached. 

Strabismus  may  exist  when  to  all  appearances  the  motor  mus- 
cles of  each  eye  are  all,  so  far  as  contractile  ability  is  concerned,  in 
a  normal  state.  The  power  of  each  muscle  to  rotate  the  eye  to  which 
it  is  attached  may  be  complete,  and  each  eye  may  turn  in  all  ordi- 
nary directions,  yet  the  visual  axes  may  deviate  to  the  extent  that 
double  vision  may  be  present,  and  even  to  such  a  degree  that  the 
deviation  of  one  of  the  eyes  may  be  a  conspicuous  defect.  On  the 
other  hand,  strabismus  occurs  because  one  or  more  of  the  muscles  of 


1  Anom.  of  Accom.  and  Refract.,  p.  244. 


356  ANOMALIES  OF  MOTOR  MUSCLES. 

the  eyes  is  disabled  or  because  there  is  some  mechanical  obstruction 
to  the  free  movement  of  one  or  both  eyes  in  certain  directions.  It  is 
evident  that  these  two  classes  of  conditions  divide  the  cases  of  strabis- 
mus into  two  distinct  classes.  In  the  first  class  the  motility  of  the 
eyes  is  complete,,  while  in  the  other  class  the  movements  are  more  or 
less  restricted.  The  first  class  has,  since  the  writings  of  von  Graefe 
on  the  subject  of  strabismus,  been  known,  as  already  stated,  under 
the  designation  of  concomitant  strabismus.  In  the  present  classi- 
fication it  is  called  heterotropia.  The  other  form,  usually  known  as 
paralytic  strabismus,  is  here  known  as  colytropia. 

Each  class  of  strabismic  deviations  is  manifest  under  different 
forms. 

Concomitant  strabismus  (heterotropia)  has  the  forms  of  con- 
verging, diverging,  sursumvergent,  and  deorsumvergent  strabismus 
— or,  according  to  the  present  classification,  the  class  heterotropia, 
in  which,  if  the  visual  line  of  one  eye  is  fixed  upon  a  given  point 
within  the  ordinary  range,  the  other  visual  line  fails  to  meet  it  at 
the  point  of  regard  and  is  therefore  directed  to  some  other  point,  is 
divided  into  specific  forms,  as  is  the  case  with  heterophoria  described 
in  Section  XXXIII. 

Buffon  and  others  considered  strabismus  cases  as  divided  into  three 
degrees  of  intensitjr,  according  to  what  was  believed  to  be  the  visual  force  of 
the  retina.  Thus,  for  Buffon,  a  difference  of  what  he  considered  three-tenths 
of  the  force  of  the  eyes  constituted  the  first  degree.  This  slight  degree  was. 
called  by  this  author  faux  trait  de  la  vue.  This  slight  form  is  probably  the 
same  as  the  "insufficiency  of  the  interni"  of  von  Graefe. 

In  the  second  degree  the  strabismus  is  more  manifest  and  is  the  most 
frequent  form. 

The  third  degree  is  characterized  by  an  entire  deviation  of  the  cornea, 
behind  the  inner  canthus. 

In  all  forms  of  concomitant  strabismus,  with  possible  exceptions 
in  anotropia  and  katotropia,  there  is  diplopia  which  may  or  may 
not  be  consciously  recognized  by  the  subject  of  the  defect.  This 
diplopia  can,  however,  in  nearly  all  cases,  be  recognized  by  the  strabis- 
mic person  after  repeated  trials  under  proper  circumstances.  After 
recognition  has  been  once  accomplished,  it  is  usually  very  easy  to  be 
observed,  and  requires  only  the  volition  of  the  squinting  subject  to 
present  the  double  images  to  the  consciousness. 

In  the  condition  in  which  it  is  not  recognized  there  is  a  mental 
suppression  of  the  image  of  the  deviating  eye  which  through  long. 


HETEROTROPIA.  357 

habit  becomes  a  fixed  mental  characteristic.1  So  complete  may  be 
the  failure  of  the  squinting  eye  to  recognize  its  image  that,  even  when 
the  usually  fixing  eye  is  covered,  it  fails  to  locate  the  position  of 
objects  in  the  field  of  vision  or  even  to  acknowledge  the  sensation  of 
vision  to  a  degree  sufficient  to  perceive  even  bright  objects.  Such 
extreme  amblyopia  may  be  present  in  eyes  in  which  the  ophthalmo- 
scope fails  to  reveal  the  slightest  indication  of  disease  and,  as  we  shall 
see  as  we  advance,  in  eyes  which  are  in  fact  in  perfect  physical  health. 

In  its  effects  upon  the  physiognomy  strabismus  varies  from  a 
slight  defect  which  may  only  add  piquancy  to  the  expression  to  a 
conspicuous  deformity  which  is  disagreeable  or  repugnant  according 
to  its  form  and  degree.  In  the  form  known  in  the  last  century  under 
the  name  of  strabismus  horrible,  in  which  one  eye  deviated  up  and 
the  other  down,  the  expression  is  extremely  repellant. 

That  such  a  defect  should  seriously  compromise  the  prospects  of 
the  possessor  is  too  evident.  For  not  only  is  the  physical  effect  un- 
favorable, but  the  mental  and  moral  state  of  the  strabismic  person 
is  often  unfavorably  influenced. 

The  effect  of  the  deformity  upon  the  health  of  the  subject  has 
been  discussed  elsewhere.  That  some  strabismics  who  acquire  the  art 
of  effectually  suppressing  the  mental  appreciation  of  the  image  of 
the  squinting  eye  remain  in  good  health  until  a  somewhat  advanced 
period  in  life  does  not  invalidate  the  general  rule  that  strabismus 
leads  to  early  exhaustion  of  the  powers  of  the  patient,  and  that  but 
a  small  proportion  of  strabismic  persons  reach  the  age  known  as 
middle  life.  Strabismic  children  are  seen  in  much  greater  numbers 
than  adults  who  squint,  and  the  difference  is  only  in  part  due  to  the 
results  of  corrective  operations. 

The  effect  on  the  quality  of  vision  is  also  manifest.  The  visual 
sense  of  relief  (projection)  such  as  is  obtained  by  binocular  vision 
is  largely  absent. 

The  power  of  vision  of  the  deviating  eye  is  usually  seriously 
impaired  and  sometimes  practically  lost,  while  the  visual  acuteness 
of  the  apparently  healthy  eye  is  generally  reduced. 


xMore  properly,  it  is  a  failure  to  interpret  the  muscular  actions  which 
direct  the  position  of  the  eye. 

The  eye  not  trained  to  interpret  these  muscular  actions  has  no  ability 
to  determine  the  forra  or  even  the  location  of  objects  in  the  field  of  vision. 

This  view  of  the  "amblyopia"  of  strabismus  will  be  developed  further 
on  in  this  Section. 


358  ANOMALIES  OF  MOTOR  MUSCLES. 

The  effect  upon  the  carriage  and  gait  of  the  strabisraic  is  some- 
times notable,  although  in  some  cases  no  striking  peculiarity  is 
observed. 

In  the  early  stages  of  either  form  of  heterotropia  there  may  be 
a  variation  of  the  degree  to  which  the  defect  is  manifested,  and  in 
some  instances  the  eyes  appear  normal  at  times  and  converging  or 
diverging  at  other  times.  In  general,  squinting  disappears  during 
sleep  or  during  the  narcosis  induced  by  chloroform  or  ether.  In  fact, 
even  in  very  pronounced  and  persistent  cases  of  strabismus  the  defect 
usually  disappears  entirely  when  the  subject  of  the  strabismus  is 
under  the  influence  of  these  anaesthetics. 

In  a  proportion  of  cases  the  defect  alternates  between  the  two 
eyes.  One  eye  will  deviate  a  part  of  the  time,  to  be  succeeded  in  its 
strabismic  position  presently  by  the  other.  These  alternations  may 
occur  from  day  to  day  or  from  minute  to  minute. 

In  those  cases  in  which  the  deviation  is  confined  mostly  or 
wholly  to  one  eye,  it  is  not  because  the  defect  is  confined  to  that  eye, 
for  that  is  common  to  the  two  eyes.1 

In  all  cases  of  concomitant  squint,  if  circumstances  render  it 
more  convenient  for  the  squinting  eye  to  become  the  eye  for  fixation, 
its  fellow,  which  was  before  the  "straight"  eye,  at  once  assumes  the 
role  of  the  strabismus. 

Thus  if  the  usually  fixing  eye  is  covered,  the  habitually  deviat- 
ing eye  at  once  becomes  the  fixing  eye  and  the  other  deviates  in  a 
direction  and  to  an  extent  exactly  corresponding  to  that  of  the  lately 
deviating  eye.  If,  for  example,  the  fixing  eye  is  emmetropic,  or  nearly 
so,  placing  before  it  a  strong  cylinder  or  a  strong  concave  glass  wrill 
often  change  it  from  the  fixing  to  the  deviating  eye,  providing  that 
the  adjustment  of  the  glass  reduces  the  power  of  vision  below  that 
of  the  deviating  eye. 

In  a  great  majority  of  cases  one  eye  is  selected  for  habitual  fixa- 
tion, while  the  other  is  as  habitually  permitted  to  deviate.  The 


3  At  the  time  when  I  first  urged  this  principle  (see  Archives  Ophthalmol- 
ogy, 1889,  etc.),  it  was  accepted,  so  far  as  I  am  aware,  by  no  one.  It  has  now 
come  to  be  an  accepted  doctrine  with  many,  yet  in  the  writings  of  those  who 
have  come  to  its  acceptance  its  teachings  are  largely  if  not  wholly  ignored. 
For  example,  it  is  of  little  consequence  that  the  view  that  the  strabismic  defect 
is  divided  between  the  two  eyes  is  held,  if  all  the  treatment  to  the  lateral  mus- 
cles is  bestowed  upon  one  eye.  Some  authors  who  concede  that  strabismus  is 
common  to  the  two  eyes  insist  on  treating  the  defect  by  a  setting  back  of  the 
muscle  toward  which  the  eye  deviates  and  advancing  that  from  which  it  turns. 
Such  treatment  is,  of  course,  absolutely  inconsistent  with  the  view  that  the 
affection  is  not  confined  to  the  squinting  eye. 


HETEROPHORIA.  359 

choice  is  usually  made  with  regard  to  the  comparative  fitness  of  the 
eyes  for  distinct  vision  or  with  reference  to  the  comparative  facility 
of  adjustment  of  the  declination.  Moreover,  one  eye  may  be  so  ad- 
justed that  with  the  minimum  of  nervous  energy  it  is  directed  in  the 
horizontal  plane,  while  the  other  is  so  adjusted  that  under  like  cir- 
cumstances it  would  be  directed  at  an  angle  materially  above  or  below 
that  plane.  Then,  if  there  is  no  notable  difference  in  the  visual  pow- 
ers of  the  two  eyes  or  in  the  difficulty  of  adjusting  the  meridians,  it 
will  be  the  eye  best  adjusted  for  fixing  the  objects  within  the  field  of 
regard,  that  is,  it  will  be  the  eye  adjusted  to  the  horizontal  plane 
which  becomes  the  habitually  fixing  eye.  It  thus  happens  not  very 
rarely,  that  an  eye  with  nearly  the  normal  refraction  will  be  the 
deviating  eye,  while  one  with  a  pronounced  astigmatism  or  other 
refractive  defect  will  be  habitually  used  in  fixation.  It  is  in  such 
cases  a  question  between  clear  vision  and  easy  vision,  and  clearness 
may  be  sacrificed  to  ease.  Even  in  such  a  case  the  direction  of  the 
vertical  meridian  of  the  squinting  eye  may  be  the  essential  reason 
for  its  deviation. 

If  in  the  case  of  the  most  usual  forms  of  strabismus,  the  turning 
in  or  the  rolling  out  of  one  of  the  eyes,  each  eye  is  caused  to  look  far 
in  and  far  out,  it  will  be  seen  that  it  is  difficult,  if  not  impossible,  to 
determine  which  has  the  fullest  and  easiest  excursion.  In  fact,  ex- 
cept where  secondary  changes  have  occurred,  there  is,  even  in  extreme 
cases  of  deviation,  no  indication  of  a  cause  for  it  in  any  perceptible 
difference  in  these  in  and  out  excursions. 

From  the  time  that  attention  was  especially  directed  to  strabis- 
mus after  the  discovery  of  its  surgical  treatment  by  Strohmeyer  and 
Dieffenbach,  it  has  been  observed  that  in  a  large  part  of  the  cases  of 
strabismus  the  deviating  eye  does  not  turn  in  a  simple  and  direct 
manner,  but  very  often  obliquely.  The  descriptions  of  Boyer1  and 
his  figures  emphasize  this  observation.  Later  von  Graefe  announced 
as  the  result  of  close  observation  of  great  numbers  of  strabismic 
cases  that  it  is  the  rule  in  converging  concomitant  strabismus  that 
the  deviating  eye  deviates  not  only  in  but  also  up.  This  later  devia- 
tion he  believed  to  be  abolished  when  by  a  relaxation  of  the  internus 
the  eye  no  longer  turned  in. 

Some  form  of  vertical  deviation  of  the  squinting  eye  was  recognized  by 
von  Graefe,  who  declared  that  "as  a  rule  in  high  grades  of  converging  strabis- 


1  "Recherehes  sur  1'Operation  du  Strabisme."      Lucien  A.  H.  Boyer,  1842. 


360  ANOMALIES  OF  MOTOR  MUSCLES. 

mus,  there  is,  at  the  same  time,  a  deviation  upward  of  the  cornea,  so  that,  at 
its  position  in  the  inner  angle,  its  upper  part  is  brought  under  the  superior 
lid."1 

Lawrence  ("Diseases  of  the  Eye/'  1844)  also  thought  that  in  converging 
strabismus  the  squinting  eye  might  also  be  directed  a  little  up  or  down. 

Von  Graefe  believed  that  all  this  tendency  of  the  eye  to  rise  was 
abolished  as  soon  as  tenotomy  of  the  internus  permitted  the  eye  to  assume  a 
more  natural  position. 

Much  later  the  author2  of  this  work  insisted  that  these  vertical  deviations 
were  not  sympathetic,  but  that  the  relation  of  the  convergent  strabismus  to 
the  vertical  deviation  was  that  of  effect,  and  that  the  vertical  deviation  was 
the  cause  of  the  lateral  one.  In  a  later  paper3  the  principle  was  still  further 
developed. 

But  not  only  is  the  deviation  complex  in  the  direction  indicated 
by  von  Graefe,  but  in  the  opposite  sense,  for  it  not  infrequently 
happens  that  the  deviating  eye  is  also  turned  downward  as  well  as 
inward.  This  fact  was  known  to  observers  who  preceded  von  Graefe. 

There  is  still  another  class  of  deviations  to  which  attention  was 
first  called  by  myself.  In  this  class  there  is,  associated  with  the 
deviation  in  or  out,  a  well-defined  tendency  to  a  deviation  of  both  the 
squinting  and  the  non-squinting  eye  in  the  vertical  direction,  either 
up  or  down,  such  deviation  vertically  when  present  is  almost  invari- 
ably up  in  converging,  sometimes  down  in  diverging  squint. 

This  form  of  deviation  is  extremely  common.  It  is  easy  in  most 
cases  of  converging  strabismus  to  observe  this  double  deviation  up- 
ward, and  it  is  common  to  find  one  or  other  of  the  vertical  forms  of 
deviation  with  diverging  strabismus.  If  a  patient  with  converging 
strabismus  looks  at  a  distant  object,  and  if  the  observer  slips  a  visit- 
ing card  before  the  fixing  eye  while  he  watches  the  other  closely, 
he  will,  in  most  cases,  see  the  deviating  eye  move,  not  only  toward  the 
temple,  but  downward  as  the  eye  fixes  the  distant  object,  while  the 
sound  eye  will  turn  to  the  nose  and  will  rise  under  the  upper  lid. 
Then,  if  the  card  is  suddenly  changed  to  the  eye  which  has  become 
the  fixing  eye,  the  other  will  resume  its  position  by  moving  outward 
and  also  downward.  A  similar  phenomenon,  but  with  the  movement 
of  the  excluded  eye  upward  as  it  comes  into  fixation,  is  less  frequent. 

In  cases  of  strabismus  which  are  not  of  the  alternating  variety 
the  deviating  eye  is  usually  a  poor  seeing  eye.  It  is  said  to  be  am- 


1  Archiv  f iir  Ophthalmologie,  Bd.  ii,  2,  289. 

2  Stevens :      "Anomalies  of  the  Ocular  Muscles,"  Archives  of  Ophthalmol- 
ogy, 1889. 

3  Archives  of  Ophthalmology,  1891. 


AMBLYOPIA  OF  HETEROTROPIA.  361 

blyopie.  This  reduction  of  the  visual  power  is  often  very  consid- 
erable. In  a  pronounced  case  of  habitual  converging  deviation  of  one 
eye  in  a  youth  of  about  15  years,  the  visual  ability  of  the  deviating 
eye  is  usually  less  than  6/15.  There  is,  however,  no  fixed  rule  for  the 
amount  of  reduction  of  vision.  In  some  instances  in  which  the  devia- 
tion appears  constant  for  a  single  eye,  the  vision  of  that  eye  remains 
good,  while  in  other  cases,  otherwise  apparently  similar,  vision  ap- 
pears to  be  almost  abolished.  That  it  is  not  abolished  will  appear 
later,  but  the  subjects  of  the  defect,  if  asked  to  tell  whether  they  are 
able  to  see  the  flame  of  a  gas  jet  at  two  feet  while  the  "sound"  eye 
is  closed,  will  declare  that  no  light  is  seen. 

Others  will  suspect  that  the  light  is  perceived,  but  in  some  re- 
mote and  indefinite  part  of  what  should  be  the  field  of  vision. 

'A  series  of  trainings  will  teach  these  patients  that  they  can  not 
only  perceive  the  light,  but  that  they  can  locate  it.  The  question  has 
been  much  discussed  whether  the  failure  of  sight  is  congenital  or  a 
.result  of  the  deviation.  Each  side  of  the  question  has  had  its  earnest 
advocates. 

While  in  some  forms  of  strabismus  there  is  a  failure  of  the  visual 
lines  to  meet  at  any  fixed  point  of  regard  under  all  circumstances,  in 
others  there  may  occur  a  union  of  these  lines  at  the  point  of  regard 
under  certain  very  limited  circumstances.  Thus  in  the  converging 
form,  if  it  is  but  slight,  the  visual  lines  may  meet  at  the  point  of 
regard  if  this  is  very  near  to  the  eyes.  In  extreme  cases  of  inward 
deviation  this  is  not  practicable  even  at  a  near  point.  In  the  vertical 
forms  of  strabismus  also  there  may  be  a  union  of  the  lines  of  vision 
at  a  near  point,  although  at  all  points  more  remote  there  is  a  separa- 
tion. In  respect  to  the  faculty  of  convergence,  it  is  an  interesting 
fact  that  while  in  a  considerable  proportion  of  cases  in  which  the 
deviation  is  markedly  in,  and  all  the  optical  phenomena  are  distinctly 
those  of  converging  strabismus,  when  a  very  near  point  is  reached 
the  visual  lines  diverge,  and  the  extreme  point  of  convergence  of  the 
optic  axes  is  more  remote  from  the  eyes  than  the  normal  or  usual 
converging  point  of  non-strabismic  eyes.  On  the  other  hand,  there 
is  a  certain  proportion  of  those  cases  where  the  squint  is  of  a  marked 
diverging  character,  in  which  the  ability,  under  the  impulse  of  a  mo- 
mentary effort  at  convergence,  the  visual  lines  can  be  forced  to  meet 
at  a  point  very  near  to  the  eyes. 

Thus  it  would  appear  that,  at  least  in  these  cases,  the  strabismus 
is  not,  as  some  have  characterized  it,  a  manifestation  of  excess  of 


362  ANOMALIES  OF  MOTOR  MUSCLES. 

positive  or  negative  convergence.  It  has  been  said  above  that  in 
strabismus  there  is  always  cliplopia.1  This  is  true  of  all  cases  in 
which  there  is  vision  in  both  eyes,  whether  the  person  subject  to  the 
defect  is  conscious  of  it  or  not.  The  custom  established  from  the 
earliest  years  of  life  of  disregarding  the  impressions  made  upon  the 
squinting  eye  render  the  fact  no  less  real  that  impressions  are  received 
by  the  retina  of  that  eye  and  are  duly  transmitted  to  the  nervous 
centers  at  which  such  impressions  are  perceived.  That  these  impres- 
sions may  in  some  instances  convey  no  clear  idea  of  the  object  seen  is 
also  true.  In  most  cases,  by  some  practice,  the  double  images  are  per- 
ceived. In  those  in  which  the  perception  of  the  image  of  the  squint- 
ing eye  simultaneously  with  the  other  eye  is  extremely  difficult,  if 
not  impossible,  the  squint  is  notably  of  the  complicated  form,  that 
is,  it  is  not  only  in  or  out,  but  markedly  up  or  down.  Notwithstand- 
ing the  difficulties  in  recognizing  diplopia,  it  is  to  the  presence  of 
these  double  images  that  we  must  resort  for  the  most  accurate  in- 
formation respecting  the  character  and  degree  of  strabismus. 

As  a  rule  the  location  of  these  images  is  an  accurate  index  to 
the  direction  of  the  squint.  Yet,  as  will  be  seen  as  we  proceed,  the 
location  of  the  images  may  be  entirely  inconsistent  with  the  rule. 

If  the  deviation  of  the  strabismic  eye  is  in,  toward  the  other  eye, 
the  double  images  are  liomonymous,  that  is,  each  image  is  seen  on 
the  same  side  as  the  eye  which  perceives  it.  The  right  image  is  seen 
by  the  right  eye,  the  left  by  the  left  eye.  If  the  deviating  eye  turns 
away  from  its  fellow,  the  diplopia  is  lieteronymous.  The  images 
are  crossed.  That  seen  by  the  right  eye  is  on  the  left  side  and  that 
seen  by  the  left  eye  is  at  the  right. 

If  the  optic  axis  of  the  deviating  eye  turns  above  that  of  the 
other,  the  image  seen  by  the  upward  deviating  eye  is  directed  below 
that  of  the  fixing  eye.  If  the  axis  is  directed  below  that  of  the  fixing 
eye,  its  image  is  higher  than  the  eye  which  is  engaged  in  fixation. 

A  moment's  consideration  of  the  optical  principles  involved  in 
these  various  positions  of  the  eyes  and  their  images  will  render  the 
reasons  clear. 

Let  it  be  first  supposed  that  the  images  of  objects  fall  upon  the 
retina  of  a  single  eye.  The  objects  are  first  supposed  to  be  at  the 
same  height,  one  at  the  right,  the  other  at  the  left  of  a  point  at  which 


3  Of  course,  this  proposition  assumes  that  visual  faculty  is  present  in  both 
eyes.  There  are  cases  of  very  marked  strabismus  in  which  one  eye  is  entirely 
blind.  Of  course,  in  such  cases  there  can  be  no  binocular  diplopia. 


DIPLOPIA  OF  STRABISMUS.  363 

the  eye  is  fixed.  Let  a  (Fig.  145)  be  the  point  of  fixation  and  b  and 
c  the  two  objects  in  the  horizontal  plane.  The  image  of  b.,  the  left 
hand  image,  is  perceived  at  b',  which  is  at  the  right  of  the  macula 
lutea,  and  the  image  of  c,  the  right  hand  object,  is  perceived  at  the 
point  of  c',  which  is  at  the  left  of  the  macula.  The  image  of  c,  the 
right  hand  object,  is  perceived  by  a  point  of  the  retina  at  the  left  of 
the  point  where  the  left  hand  object  is  perceived.  Hence,  if  an  image 
is  impressed  at  a  point  in  the  retina  which  is  at  the  right  of  the  point 
at  which  another  image  is  impressed,  that  which  forms  its  impression 
at  the  right  is  mentally  attributed  to  the  left,  and  the  object  is,  in 
the  judgment  of  the  person  to  whom  the  eye  belongs,  located  at  the 
left  of  the  other  object. 

According  to  the  law  of  corresponding  points,  the  point  c'  in  one 
retina  will  be  removed  in  the  horizontal  meridian  of  the  retina  as 


Fig.  145. 

far  to  the  left  as  its  corresponding  point  in  the  other  retina.  Ac- 
cordingly, if  the  point  c'  in  one  eye  is  at  the  temporal  side  of  the 
macula,  the  point  c'  in  the  other  eye  will  be  at  the  nasal  side  of  the 
macula,  and  they  will  be  equally  removed.  A  corresponding  rule 
would  hold  if  the  images  of  both  objects  were  perceived  at  the  nasal 
or  temporal  side  of  the  retinas.  If  the  distance  be  is  represented  by 
the  distance  b'c'  in  the  retina,  then  if  the  images  were  received  upon 
the  two  retinas,  the  distances  of  b'  and  c'  from  the  macula  on  the 
temporal  side  of  one  eye  would  equal  the  distance  of  b'  and  c'  from 
the  macula  on  the  nasal  side  of  the  other.  Applying  this  principle 
let  a,  Fig.  146,  be  an  object  seen  by  both  eyes.  If  one  eye,  the  right, 
fixes  the  object,  the  image  will  be  perceived  at  the  macula  m.  Suppose 
the  other  eye,  the  left,  to  deviate  inward.  Then  the  image  of  a  will  not 
be  produced  at  m,  but  at  n,  which  is  at  the  right  of  the  macula.  Ac- 


364  ANOMALIES  OF  MOTOR  MUSCLES. 

cording  to  the  principle  already  shown  the  image  of  a  perceived  at 
the  retina  at  n  will  be  mentally  located,  not  at  the  right,  but  far  at 
the  left  of  a,  at  a'. 

Thus  it  appears  that  although  a  projection  of  the  optical  axes 
inward  would  result  in  a  crossing  of  these  imaginary  lines  the  posi- 
tion of  the  images  is  in  fact  not  crossed  and  the  image  seen  by  the 
deviating  eye  never  even  reaches  to  the  image  seen  by  the  fixing  eye, 
but  remains  on  the  same  side  as  the  deviating  eye.  That  is,  the  images 
are  seen  liomonymously  (  O/AOS,  common;  owp.a.  name,  the  same 
side). 

Quite  different  is  it  when  the  deviation  of  the  strabismic  eye  is 
divergent,  for  then,  although  the  optic  axes  point  away  from  each 


Fig.  146. 

other,  the  images  are  crossed  and  are  said  to  be  seen  heteronymously 
(Ire/aos,  different). 

Bearing  in  mind  the  phenomena  shown  in  Fig.  145,  it  will  be 
seen  that  if  the  right  eye  is  in  fixation  while  the  left  deviates  out- 
wardly, the  impression  from  the  object  a  will  fall,  in  the  left  eye,  at 
a  point  of  the  retina  situated  at  the  temporal  side  of  the  macula 
lutea.  It  will  be  seen  then,  not  at  the  left  hand  side,  but  at  the  right 
of  the  image  of  the  eye  in  fixation,  and  the  distance  will  be,  as  in  the 
figures  measured  by  the  distance  of  the  point  c'  from  the  macula  of 
the  left  eye. 

We  may  also  apply  the  principle  shown  in  Fig.  145  to  the  loca- 


LOCATION  OF  IMAGES.  365 

tion  of  images  in  cases  of  deviation  of  the  images  in  a  vertical  direc- 
tion. Let  the  diagram  (Fig.  145)  represent  a  section  of  the  eye 
in  a  vertical  direction,  and  let  the  objects  a,  c  be  no  longer  in  the 
horizontal,  but  in  a  vertical  plane  with  each  other — and  suppose  a  is 
in  the  primary  plane  while  b  is  above  this  plane  and  c  below  it.  Then 
will  the  impression  of  a  be  received  at  the  macula,  that  of  6  at  a  point 
in  the  retina  situated  below  the  macula,  and  that  of  c  at  a  point  above 
the  macula. 

Returning  to  the  appearances  of  an  object  as  seen  by  the  two 
eyes  when  the  axis  of  one  deviates  above  or  below  the  other,  suppose 
that  the  image  a  is  seen  by  the  fixing  right  eye,  the  image  being  per- 
ceived at  the  macula,  and  that  the  object  d  is  seen  by  the  left  eye, 
the  optic  axis  of  which  deviates  above  that  of  the  right.  Then  will 
the  impression  of  the  object  a  fall,  not  upon  the  macula  of  the  left 
eye,  but  above  it.  The  image  seen  by  the  left  eye  then  will  be  seen 
not  above  that  of  the  fixed  eye  as  might  be  imagined,  but  below  it  as 
is  shown  at  c,  c'  (Fig.  145).  On  the  same  principle,  if  the  optic 
axis  of  the  left  eye  should  deviate  below  the  line  of  the  optic  axis  of 
the  fixing  right  eye,  the  image  will  be  seen  above  as  at  b,  b'. 

It  need  hardly  be  added  that  if  the  deviations  are  in  compound 
directions,  as,  for  example,  upward  and  outward  or  downward  and 
inward,  the  position  of  the  images  will  be  influenced  by  each  of  the 
elements  of  the  compound  deviation. 

Although  the  principles  which  have  just  been  mentioned  govern 
in  the  great  majority  of  cases  and  are  the  rule,  there  are  certain  anom- 
alous positions  of  the  images  which  demand  attention  and  to  which 
false  interpretations  have  sometimes  been  given. 

It  sometimes  happens  that  a  person  having  an  actual  diverging 
strabismus  will,  if  caused  to  recognize  his  diplopia,  insist  that  he 
sees  the  images  homonymously,  and,  on  the  other  hand,  while  a  con- 
verging strabismus  is  actually  present,  the  patient  will  describe  the 
positions  of  the  images  as  crossed,  as  though  the  phenomena  arose 
from  a  diverging  squint.  These  phenomena  appear  perplexing,  espe- 
cially when  the  axes  of  the  two  eyes  have  not  the  appearance  of  great 
divergence  or  convergence.  The  anomaly  only  presents  itself  in  cases 
in  which  there  is  not  only  the  lateral,  but  a  distinct  vertical  deviation, 
as  well  as  an  extreme  declination,  and  as  a  general  rule,  -to  which 
there  are  some  exceptions,  is  observed  after  an  operation  for  the  cor- 
rection of  the  lateral  deviation,  in  which  the  difference  of  height  of 
the  images  or  the  extreme  declination  has  been  ignored. 


306  ANOMALIES  OF  MOTOR  MUSCLES. 

A  second  anomaly  in  the  position  of  the  images  is  the  appear- 
ance of  more  than  one  image  in  one  of  the  eyes.  Then  it  may  happen 
that  while  the  usually  fixing  eye  will  see  the  image  normally,  the 
deviating  eye  will  see  two  and,  in  rare  cases,  even  three  images  of  the 
object.  This  class  of  cases  of  monocular  diplopia  has  no  relation  to 
the  monocular  multiplicity  of  images  which  may  be  induced  by 
notable  errors  of  refraction,  the  doubling  or  tripling  of  images  in 
cases  of  astigmatism  or  the  multiple  images  of  presbyopia.  The 
multiple  images  under  consideration  are  independent  of  any  fault  of 
refraction  or  accommodation,  and  may  occur  in  perfectly  emme- 
tropic  eyes. 

In  every  case  in  which  multiple  images  of  this  class  occur  there 
is  a  vertical  as  well  as  a  horizontal  deviation  of  the  eyes.  In  the 
majority  of  cases  also,  if  not  in  all  cases,  the  strabismus  is  to  a  certain 
extent  alternative. 

In  explanation  of  the  phenomena  it  has  been  said  of  the  first 
that  the  macula  lutea  is  located  in  a  false  position,  or  that,  from  long 
custom,  a  new  point  has  assumed  the  function  of  the  macula ;  of  the 
other  phenomenon  that,  while  the  original  macula  retains  its  func- 
tions, a  second  or  even  a  third  point  has  become  developed  as  a  new 
center  for  vision.  Both  these  hypotheses  are  alike  unsupported  by 
any  facts  which  can  be  learned  by  any  physical  examinations  or  by 
any  evidence  of  either  a  physiological  or  psychological  character. 
Both  are  assumptions  to  the  establishment  of  which  no  attempt  ap- 
pears to  have  been  made  to  reconcile  them  to  any  doctrine  of  mental 
or  physical  science. 

Without  doubt  these  eyes  are  anatomically  normal.  The  condi- 
tions are  not  metamorphoses  which  arise  from  disease.  The  most 
careful  scrutiny  of  my  own  cases  has  failed  to  detect  the  slightest 
defect  in  the  fundus  of  the  eyes  of  those  subject  to  either  of  the 
anomalies.  And  this  has  been  the  testimony  of  others. 

Our  inquiry  into  the  character  of  the  cases  and  into  the  visual 
phenomena  will,  I  think,  classify  each  of  these  anomalous  conditions 
as  the  normal  manifestations  of  abnormal  physical  relations. 

In  order  to  understand  the  reasons  for  these  conditions  it  is 
necessary  to  recall  the  theory  of  spatial  sight — ideas  with  reference 
to  the  location  of  visual  impression,  and  their  reciprocal  relations 
of  direction  and  distance.  The  phenomena  of  vision  teach  that  these 
spatial  ideas  have  for  their  basis  the  energy  which  is  applied  to  the 
motor  impulses  of  the  eyes.  Eelative  distances  and  directions  in  the 


MULTIPLE  IMAGES.  367 

field  of  vision  arc  the  expressions  of  the  motion  required  to  pass  the 
retinal  space  separating  the  point  at  which  two  impressions  are 
formed.  The  ideas  then  of  relative  distances  become  intimately  asso- 
ciated with  certain  motor  impulses.  If  the  two  eyes  are  in  equilib- 
rium, if  they  can  move  in  such  a  manner  that  the  image  of  an  object 
may  be  perceived  at  corresponding  points  of  the  two  eyes,  there  is 
binocular  vision.  But  if,  as  a  result  of  strabismus,  especially  of  an 
alternating  character,  a  new  faculty  of  estimating  spatial  relations 
has  been  acquired,  an  image  may  be  "projected"  in  a  direction  which 
will  be  essentially  different  from  the  usual  and  normal  projection, 
and  when,  by  introducing  at  the  same  moment  the  estimation  formed 
by  the  normal  movements  and  that  formed  by  the  acquired  experience 
two  different  space  ideas  are  presented  to  the  mind  simultaneously, 
the  mental  projection  corresponds  with  the  two  forms  of  experience. 

An  eye  adjusted  so  that  it  is  able  at  times  to  assume  the  faculty 
of  fixation  and  ready  at  other  times  to  abandon  it  to  the  other  eye, 
maintains  on  the  one  hand  an  ability  to  estimate  correctly  distances 
and  directions  by  the  position  of  the  impression  on  the  retina  rela- 
tively to  the  position  of  the  macula.  It  may  also  acquire  during 
its  exclusion  from  fixation  an  ability  to  make  somewhat  similar  esti- 
mates, starting  from  fixed  points  outside  the  macula,  but  which  in 
the  position  of  deviation  may  occupy  positions  corresponding  to  those 
of  the  macula  of  the  fixing  eye.  Under  certain  circumstances,  when 
the  images  of  the  two  eyes  are  brought  strongly  to  the  consciousness, 
both  these  estimates  are  taken  into  account,  and  the  image  of  the  eye 
which  has  acquired  the  new  faculty  is  consequently  located  in  two 
positions.  If  the  eye  which  has  but  one  image  is  excluded  from  the 
act  of  vision,  the  second  image  of  the  eye  having  monocular  diplopia 
disappears. 

The  phenomenon  is  analogous  to  that  in  the  familiar  experiment 
of  crossing  two  fingers  of  one  hand  and  passing  between  the  fingers 
thus  crossed  a  small  body  like  a  playing  marble,  when  the  object  is 
felt  like  two  bodies,  the  spatial  position  of  each  being  attributed  to 
the  point  from  which  the  sensation  is  usually  experienced. 

The  following  is  a  typical  case  of  monocular  diplopia : — 

Bessie  — ,  aged  13  (1882),  emmetropia.  Under  influence  of  atropine 
H^Yso-  Is  weak,  nervous  and  has  headache.  Moderately  marked  con- 
verging strabismus  with  vertical  diplopia  (right  hypertropia  15°).  The  con- 
verging squint  alternates  between  the  two  eyes. 

If  a  red  glass  is  placed  before  the  right  eye  three  images  are  seen,  two 
of  which  are  red  and  are  nearly  horizontal  with  each  other,  the  other  white, 


368  ANOMALIES    OF   MOTOR    MUSCLES. 

which  is  much  above  the  red  images.  If  a  prism  of  1°  with  its  base  down  is 
now  placed  before  the  right  eye,  thus  only  partly  correcting  the  height  of  the 
images,  the  white  is  between  the  red  images,  but  still  somewhat  above  them. 

Tenotomies  of  the  superior  rectus,  right  eye,  and  of  the  internus  of  each 
eye  corrected  the  strabismus  so  that,  while  the  patient  gazed  at  a  distant 
object  directly  in  front  of  her,  a  card  slipped  alternately  before  each  eye  gave 
rise  to  no  deviation  in  exclusion  and  all  the  movements  of  the  eyes  were  free 
and  normal. 

Still  with  the  red  glass  before  one  eye,  there  remained  a  second  image 
faintly  seen  at  one  side,  but  no  longer  a  third,  as  before.  Thus,  the  images 
apprehended  at  the  macula  of  the  two  eyes  were  perfectly  blended,  but  there 
remained  the  second  image  of  the  right  eye.  If,  by  means  of  a  strong  prism 
placed  with  its  base  up  or  down  before  either  eye  so  as  to  cause  the  images  seen 
at  the  macula  to  separate,  the  right  eye  again  saw  two  images  and  the  left 
one.  But  if  the  left  eye  ictis  covered,  only  a  single  image  was  seen  by  the 
right  eye.  After  some  months  the  supernumerary  image  of  the  right  eye 
disappeared. 

The  entire  disappearance  of  the  second  image  of  the  right  eye 
(which  appeared  before  the  correction  of  the  strabismus  as  well  as 
after  it)  when  the  left  eye  was  excluded  from  vision,  shows  that  the 
second  image  was  entirely  relative  to  the  position  of  the  image  of 
the  left  eye.  In  fact,  it  was  an  unconscious  conclusion  that  the  object 
should  appear  in  a  certain  direction,  since  a  certain  movement  of  the 
eye  would  be  required  to  place  the  point  of  the  retina  at  which  the 
visual  sensation  was  felt  in  correspondence  with  the  macula  of  the 
left  eye. 

And  here  we  may  return  to  the  question  of  the  amblyopia  in 
strabismus,  of  which  mention  has  already  been  made  at  page  361. 
The  same  principles  prevail,  but  in  the  case  of  entire  abandonment  of 
efforts  to  direct  one  eye,  especially  if  the  abandonment  occurs  at  a 
very  early  period,  the  consciousness  has  taken  no  account  of  the 
movements  of  the  eye,  and  the  relations  between  space  and  motion, 
so  far  as  they  have  ever  existed  by  native  and  inherent  intuition  or 
by  very  early  acquired  experience,  have  been  so  completely  lost  that 
the  mind  forms  no  conception  of  form  or  space  from  their  move- 
ments. This  extreme  condition,  although  rare,  is  occasionally  met 
with.1 

If  occasion  demands  that  the  movements  of  the  amblyopic  eye 
should  be  observed  and  estimated,  the  experience  gained  by  the  other 
eye  is  brought  into  service  and  the  amblyopic  eye  soon  acquires  the 


1  This  discussion  should  be  read  in  connection  with  the  section  on  "Visual 
Perception  of  Space,"  page  124. 


STRABISMJC  AMBLYOPIA  NOT  CONGENITAL.  369 

faculty  of  estimating  form  and  space.  A  most  striking  example  illus- 
trating this  statement  is  found  in  the  remarkable  case  reported1  by 
Dr.  Walter  B.  Johnson.  In  this  case  the  eyes  of  the  patient  had  been 
examined  by  Dr.  Johnson  a  few  days  previous  to  an  injury  when  it 
was  found  that  the  vision  of  the  right  eye  was  20/lr>,  and  of  the  left, 
only  ability  to  count  fingers  at  six  inches.  Xo  glass  improved  vision. 
Ten  days  later,  the  right  eye  was  destroyed  by  an  accident.  Six 
months  later  the  amblyopic  left  eye  had  20/15  vision  without  glasses. 

Certain  authors  have  assumed  that  the  amblyopia  of  squint  is 
congenital,  and  that  it  is  a  predisposing  element  of  the  latter. 

In  adopting  this  assumption  one  must  take  the  ground  that  the 
visual  sense  of  space  is  wholly  and  always  a  connate  possession  of 
the  visual  organs — that  it  is  an  inborn  characteristic  inseparable  from 
healthful  eyes.  Those  who  have  assumed  this  dogma  have  perhaps 
neglected  to  examine  the  problem  of  spatial  discrimination  by  the 
eyes  and  its  development. 

In  the  amblyopic  eye,  from  strabismus,  we  have  all  the  physical 
possibilities  of  space  perception  without  the  mental  process  of  dis- 
crimination. So  completely  may  the  mental  process  be  in  abeyance 
that  no  borders  of  objects,  even  very  conspicuous  ones,  may  be  recog- 
nized. Such  an  eye,  as  in  the  case  of  Dr.  Johnson,  fails  to  recognize 
any  object  and  in  many  instances  even  the  location  of  the  illuminating 
flame  of  a  candle  in  a  darkened  room,  yet  it  has  suffered  from  no 
disease  and  is  anatomically  fully  developed.  It  is  not  a  weak  eye, 
or  an  imperfect  one.  It  is  undoubtedly  the  fact  that  in  such  a  case 
as  has  been  mentioned,  the  local  signs  of  space  ideation  have  always 
been  present,  but  without  the  mental  interpretations  of  those  signs 
they  are  not  operative,  and  they  remain  a  chaos  of  light  impressions 
destitute  of  significance. 

In  order  to  properly  appreciate  the  absence  of  visual  sense  in 
amblyopia  ex  anopsia  one  must  divest  himself  of  the  idea  so  com- 
monly entertained,  that  the  visual  sense  is  simply  the  consciousness  of 
a  picture  painted  on  the  retina.  As  a  matter  of  fact  the  consciousness 
of  the  form  and  position  of  objects  derived  from  the  visual  sense  is 
formed  by  the  expenditure  of  force  in  the  movements  of  the  eye  or 
in  the  recognition  of  the  force  and  direction  of  the  force  which  would 
be  necessary  to  effect  the  required  movements  of  the  eye  in  order  to 
follow  the  boundaries  of  the  object  seen  or  to  pass  from  one  object 


1  "Transactions  of  the  American  Ophthalmological  Society,"  1893. 


370  ANOMALIES   OF   MOTOR   MUSCLES. 

to  another.  These  mental  measurements  are  possible  only  as  the 
result  of  experience,  and  the  eye,  between  which  and  the  mind  no 
system  of  precise  estimation  of  such  movements  has  been  established, 
is  to  all  intents  a  blind  eye,  notwithstanding  the  fact  that  its  parts 
are  in  perfect  health  and  the  rods  and  cones  of  its  retina  are  as  sus- 
ceptible to  the  influence  of  light  waves  as  the  eye  which  is  able  to 
appreciate  all  the  stimuli  of  light.  In  this  respect  we  make  a  some- 
what rude  comparison  with  another  form  of  muscular  movement,  with 
the  condition  that  we  must  reverse  the  course  of  the  influence  of 
cause  and  effect. 

One  who  may  be  a  facile  penman,  able  not  only  to  write  but  to 
write  with  speed  and  elegance,  suddenly  loses  the  ability  to  use  the 
right  hand.  This  person  can  in  the  mind  form  images  of  letters  and 
words,  and  his  remaining  left  hand  is  in  all  respects  physically  ca- 
pable of  performing  all  the  movements  of  writing,  yet  he  finds  that 
he  is  now  unable  even  to  form  his  own  signature  except  perhaps  in 
ungraceful  and  unaccustomed  characters. 

In  what  lies  the  disability  of  this  left  hand  to  form  the  char- 
acters which  were  so  easily  formed  by  the  right  hand? 

It  lies  in  the  absence  of  experimental  relations  between  the  mind 
and  the  muscles  of  that  hand.  A  week  of  practice  may  render  this 
uneducated  hand  facile  with  the  pen. 

In  this  case  we  have  the  absence  of  the  ability  on  the  part  of 
the  mind  to  direct  the  movements  of  the  hand  through  absence  of 
experience  in  sending  messages  to  the  organ;  in  the  other  we  have 
the  absence  of  ability  to  interpret  the  movements  by  reason  of  inex- 
perience in  such  interpretations,  a  fact  which  leads  to  inability  to 
direct  the  movements. 

Even  the  most  amblyopic  eyes  may  attain  to  at  least  an  approxi- 
mate estimation  of  form  and  space  even  although  the  strabismus  is 
uncorrected.  The  following  case  will  serve  as  an  illustration  of 
this  :— 

Mr.  V.,  aged  59,  consulted  me  in  1893  on  account  of  a  moderate 
diverging  strabismus.  It  was  evident  that  the  deviating  eye  turned 
upward  more  than  outward.  The  strabismic  eye  was  totally  ambly- 
opic. There  was  a  vague  perception  of  light,  but  no  sense  of  form 
or  space.  A  lighted  candle  held  within  four  feet  of  the  eye  when  the 
other  was  covered  gave  an  impression  of  a  strong,  yellowish,  diffused 
light,  but  suggested  no  form  of  a  flame  nor  direction  from  which  the 
light  came.  The  eye  was  to  all  appearances,  when  examined  by  the 


MEANS  OF  DETERMINING  DIRECTION  OF  STRABISMUS.        371 

ophthalmoscope,  perfectly  healthy,  and  its  refraction  nearly  em- 
metropic.  I  determined  to  educate  the  eye  to  the  perception  of 
space.  Commencing  by  blindfolding  the  well  eye  and  allowing  the 
patient  to  touch  the  candlestick,  I  succeeded  after  two  days  in  obtain- 
ing a  vague  recognition  of  the  indistinct  form  of  the  candle  flame, 
which  appeared  like  a  large  ball  of  light  in  some  undetermined  part 
of  the  visual  field,  generally  far  to  one  side,  but  never  in  its  proper 
location.  After  several  days  more  I  was  able  to  obtain  rather  un- 
satisfactory tests  with  prisms,  and  before  two  weeks  had  passed  the 
patient  could  make  somewhat  unsatisfactory  tests  with  the  phorome- 
ter,  the  image  of  the  candle  flame  of  the  deviating  eye  appearing 
nearly  as  distinct  as  the  other,  but  changing  in  position  from  one 
relation  to  another  with  the  best  image. 

The  patient  left  with  the  promise  to  return  for  more  tests  and 
finally  for  treatment,  but  I  did  not  see  him  again. 

When  it  happens  that  by  any  means  the  non-squinting  eye  is 
rendered  useless  or  its  usefulness  is  materially  reduced,  the  habitually 
squinting  eye  may  assume  the  usual  functions  of  vision  and  the  other 
may  become  amblvopic.1 

The  means  of  determining  the  presence  of  strabismus,  and  its 
direction  and  extent  include: — 

The  general  appearance  of  marked  deviation  of  one  eye. 

The  tests  by  deviation  in  exclusion. 

The  tests  by  diplopia  and  the  use  of  prisms,  and  the  tests  of  the 
various  rotations  of  the  eyes. 

In  marked  cases  of  lateral  strabismus  the  deflection  of  one  eye 
is  so  apparent  to  an  observer  that  a  single  glance  is  sufficient  to  estab- 
lish the  general  fact  of  a  deviation,  and  when  it  is  in  or  out  the 
general  direction,  but  in  cases  of  vertical  strabismus  which,  quite 
contrary  to  the  statements  of  some  well-known  text-books  which  state 
that  it  is  rare,  is,  in  fact,  quite  common,  the  deviation  is  not  so 
readily  detected,  and  it  is  not  rare  that  in  cases  of  vertical  strabismus 
in  which  single  vision  with  the  two  eyes  is  quite  out  of  the  question, 
not  only  is  the  defect  overlooked  by  the  friends  of  the  subject  of  it, 
but  even  ophthalmologists  not  rarely  fail  to  observe  the  fact  of  its 
existence. 

In  cases  of  lateral  deviation  also  in  which  the  strabismic  char- 
acter of  the  direction  of  the  eyes  is  plainly  seen,  yet  when  there  is 


1  See  case  reported  by  Dr.  D.  W.  Hunter,  American  Ophthalmological  So- 
ciety, 1905. 


372  ANOMALIES  OF  MOTOR  MUSCLES. 

associated  with  it,  as  there  nearly  alwa}'s  is,  a  deviation  in  the  ver- 
tical direction,  this  latter  deflection  is  almost  invariably  overlooked. 
Much  has  been  said  of  the  angle  a  or  alpha  in  connection  with  the 
diagnosis  of  strabismus,  yet  this  angle  can  have  no  important  place  in 
the  question  of  squint,  for  in  all  cases  of  so  slight  deviation  that  there 
might  be  any  possibility  of  a  question  between  the  angle  a  or  alpha 
and  a  strabismus,  the  distinction  could  be  instantly  made  by  the  test  of 
deviation  in  exclusion,  or  if  by  any  chance  a  doubt  could  still  remain, 
a  single  test  by  the  phoromcter  would  determine  the  question. 

Eeference  has  therefore  been  made  to  this  supposed  question  of 
diagnosis  only  to  assure  the  student  of  the  subject  that  the  angle  a 
is  a  subject  having  no  relation  to  the  question  of  the  presence  or 
absence  of  strabismus. 

DEVIATION  IN  EXCLUSION. 

If  the  subject  of  a  strabismus  is  directed  to  fix  his  gaze  on  an 
object,  preferably  the  flame  of  a  candle,  situated  in  the  median  and 
primary  planes  and  at  a  distance  of  about  twenty  feet,  the  examiner 
will  be  able  to  detect  any  considerable  deviation  of  the  visual  axes  by 
passing  a  visiting  card  from  in  front  of  one  eye  to  the  front  of  the 
other.  (The  use  of  the  hand  for  such  a  purpose  is  far  too  clumsy 
and  could  only  serve  in  cases  of  very  marked  turnings.) 

If  the  eyes  are  closely  observed  as  the  patient  looks  at  the  candle, 
one  of  the  eyes  may  appear  to  deviate.  The  examiner  slips  his  card 
suddenly  in  front  of  the  apparently  fixing  eye,  when,  if  the  other 
has  in  reality  not  been  in  fixation,  it  may  be  seen  to  move  in  order  to 
bring  the  optic  axis  in  line  with  the  object.  If,  however,  the  move- 
ment is  not  observed,  the  other  eye  may  be  treated  in  the  same  man- 
ner, or  several  trials  may  be  made  on  the  same  eye. 

If  the  card  is  passed  in  front  of  one  eye  and  then  in  front  of 
the  other  alternately  there  may  be  observed  a  decided  movement  of 
adjustment  of  the  eye  last  released  from  exclusion  in  order  to  bring 
it  into  fixation.  This  deviation  from  alternate  exclusion,  one  eye 
being  covered  while  the  other  is  free,  does  not  prove  a  strabismic 
condition,  for  it  may  happen  that  with  a  deviation  which  is  plainly 
perceptible  there  may  exist  the  power  and  the  habit  of  binocular 
vision.  In  the  first  case,  however,  when  with  both  eyes  free,  if  one 
is  suddenly  excluded,  the  other  must  move  in  order  to  fix  the  object, 
there  was  no  union  of  the  images  of  the  two  eyes,  and  there  existed 


TESTS  BY  DIPLOPIA.  373 

an  actual  strabismic  deviation,  even  if  the  movement  was  extremely 
slight. 

If  the  deviation  is  detected,  its  direction  in  or  out,  up  or  down 
is  to  be  carefully  observed.  It  may  be  approximately  measured  by 
neutralizing  the  movement  by  prisms.  (In  very  high  grades  of  devia- 
tions measurement  in  this  manner  is  either  unsatisfactory  or  im- 
practical.) 

Observing  the  direction,  a  prism  is  held  in  front  of  one  of  the 
eyes  while  the  card  is  pressed  alternately  before  each,  and  the  prism, 
if  not  strong  enough  to  neutralize  the  movement,  is  gradually  in- 
creased until  the  eyes  remain  fixed  as  the  card  is  moved  backward 
and  forward.  If  very  strong  prismatic  effect  is  required,  it  may,  of 
course,  be  divided  between  the  two  eyes.  If  the  direction  of  the 
squint  is  compound,  the  position  of  the  prism  may  be  adjusted  to  it 
or,  better  still,  one  prism  may  be  used  to  neutralize  the  lateral  and 
another  the  vertical  deviation. 

Even  a  degree  of  deviation  of  a  less  extent  than  is  readily  seen 
by  an  observer  may  cause  diplopia,  especially  if  the  deviation  is  ver- 
tical. In  such  a  case,  if  the  patient  himself  is  able  to  detect  a  slight 
apparent  movement  of  the  object  and  its  direction  the  prism  may 
be  used  as  before  until  the  patient  can  no  longer  detect  the  move- 
ment. This  slight  movement,  which  is  not  observed  by  the  examiner, 
can  be  detected  by  the  patient,  and  its  measurement  by  a  prism  has 
been  called  the  parallax  test  by  Dr.  Alexander  Duane.  As  a  rule  it 
is  not  necessary  to  divide  the  test,  and  a  record  of  deviation  in  exclu- 
sion should  include  all  that  can  be  learned  by  this  method. 

TESTS  BY  DIPLOPIA. 

A  much  more  important  and,  when  practical,  a  much  more  exact 
class  of  testings  of  strabismus  is  that  depending  upon  the  double 
images.  In  all  cases  of  concomitant  strabismus  in  which  the  visual 
faculty  exists  in  both  eyes  there  exists  also  diplopia.  That  a  patient 
declares  that  he  does  not  see  double,  and  that  he  persists  in  the 
declaration  in  spite  of  the  most  ingenious  methods  of  wringing  the 
confession  from  him,  does  not  alter  the  case.  There  is  double  vision 
nevertheless. 

The  fact  that,  as  we  shall  see  further  on,  the  squinting  eye  has 
squinted  up  even  long  before  it  was  observed  to  squint  in  or  out, 
means  that  as  an  almost  invariable  rule  one  of  the  eyes  in  strabismus 
has  deviated  from  a  very  early  period  of  life.  It  is  easy  then  to  under- 


374  ANOMALIES  OF  MOTOR  MUSCLES. 

stand  that  the  image  which  from  earliest  experience  has  been  neg- 
lected is  not  always  easy  to  present  to  the  consciousness. 

Notwithstanding  the  difficulty  that  sometimes  presents  itself  in 
inducing  the  patient  to  realize  the  presence  and  position  of  the  sec- 
ond image,  no  attempt  should  he  made  to  make  a  final  correction  of 
strabismus  until  the  two  images  are  located.  Contemporary  litera- 
ture shows  that  there  is  a  very  prevalent  belief  that  no  measurement 
beyond  the  linear  can  or  need  he  made.  This  is  a  radical  error  and 
no  correction  worthy  the  name  of  a  correction  of  strabismus  can  be 
made  which  does  not  have  for  its  basis  the  position  of  the  double 
images  and  the  leanings  of  those  images. 

The  proportion  of  cases  in  which,  with  sufficient  patience  and 
skill,  the  diplopia  cannot  be  made  out  before  any  step  is  taken  toward 
correction  is  small,  but  if  the  examiner  is  unwilling  to  sacrifice  time 
and  labor  to  the  investigation  he  may  be  often  disappointed. 

It  is  not  an  infrequent  experience  that  a  strabismic  patient  is 
required  to  make  long  continued  trials,  day  after  day,  for  a  whole 
week,  and  in  some  instances  for  even  a  longer  period  of  time,  for  the 
single  purpose  of  learning  the  position  of  the  double  images.  Jf  the 
patient  insists  that  he  does  not  see  double  and  is  inclined  to  become 
angry  when  kindly  assured  that  nevertheless  he  does,  he  is  to  be 
encouraged  and  to  be  told  how  and  where  to  look  for  the  second 
image.  The  lesson  should  be  practiced  in  a  darkened  room  and  the 
object  should  be  a  lighted  candle.  In  order  to  give  contrasting  colors 
to  the  images  a  red  glass  should  be  used,  generally  before  the  fixing 
eye.  By  using  strong  prisms,  alternately  before  the  two  eyes  and 
changing  in  various  manners,  the  lost  image  may  be  moved  to  one 
or  other  side  or  up  or  down,  and  of  each  change  of  position  the 
patient  should  be  informed  and  his  attention  directed  to  the  point 
in  space  at  which  the  image  is  supposed  to  appear. 

When  once  the  second  image  has  been  brought  to  the  conscious- 
ness of  the  patient  there  is  rarely  any  difficulty  in  later  trials.  The 
images  are  usually  then  located  quickly. 

So  far  as  this  examination  is  concerned  the  cases  of  strabismus 
may  be  divided  into  two  very  general  but  not  well-defined  classes — the 
moderate  cases  and  the  extreme  cases.  In  moderate  cases  the  presence 
of  diplopia  can  in  most  instances  be  made  out  and  utilized.  In  cases 
of  extreme  deviation  the  difficulties  are  sometimes  so  great  and  the 
time  required  to  demonstrate  the  diplopia  so  considerable  that  some 
means  of  simplifying  the  process  is  required.  Fortunately  by  the 


TESTS  BY  DIPLOPIA.  375 

more  recent  revelations  of  the  rotations  in  strabismus,  as  shown  by 
the  tropometer,  very  important  advances  toward  the  adjustments  of 
the  visual  lines  may  be  made  before  the  diplopia  is  revealed  to  the 
patient,  and  then  when  the  images  are  more  nearly  approximated 
and  the  eye  has  learned  to  make  more  accurate  estimates  of  its  own 
relative  position,  the  diplopia  tests  can  be  brought  into  practical 
application. 

In  the  moderate  cases,  as  soon  as  the  double  images  are  discov- 
ered their  relative  positions  are  to  be  noted.  If  the  usually  fixing 
eye  has  before  it  a  red  glass  it  is  easy  to  determine  the  image 
belonging  to  each  eye  and  its  position.  If  the  images  do  not  appear 
in  the  same  horizontal  plane  it  should  be  the  first  object  of  the  exam- 
iner to  learn  the  strength  of  a  prism  which  will  bring  both  to  the 
same  level.  Suppose  that  the  right  eye  has  before  it  the  red  glass 
and  the  patient  sees  the  yellow  flame  to  the  left  and  below  the  red 
flame.  There  is  homonymous  and  vertical  diplopia — left  hypereso- 
tropia.  Taking  a  prism  from  the  box  of  trial  glasses,  the  examiner 
places  it  with  its  base  down  before  the  left  eye,  or  up  before  the  right 
eye,  and  learns  whether  the  glass  is  sufficient  to  correct  the  difference 
of  level  or  if  it  overcorrects  it.  When  the  proper  glass  is  found  to 
bring  the  two  images  to  the  same  horizontal  plane,  the  degree  of  this 
prism  measures  in  prism  degrees,  or  diopters,  the  degree  of  left  hy- 
pertropia.  It  is  then  required  in  a  similar  manner  to  learn  the  prism 
diopters  demanded  to  bring  the  two  images  to  a  vertical  line.  If 
the  deviation  is  considerable,  prismatic  corrections  may  be  divided 
by  placing  glasses  before  each  eye.  As  in  the  other  case,  the  prism 
strength  required  to  bring  the  images  to  the  same  vertical  line  meas- 
ures the  diopters  of  esotropia.  If,  in  the  first  instance,  the  prism 
was  12°  and  in  the  second  20°,  the  record  is,  left  hypertropia,  12°  ; 
esotropia,  20°.  If  now  these  prismatic  effects  are  combined,  the  two 
images  usually  unite  as  one.  In  higher  degrees  of  deviation  the  meas- 
urements are  less  uniform,  and  the  prisms  which  measure  the  differ- 
ent elements  of  deviation  do  not  always  unite  the  images. 

In  low  degrees  of  deviation  and  with  a  readiness  to  locate  the 
images,  the  phorometer  is  by  far  the  most  convenient  and  accurate 
means  for  estimating  the  various  displacements  of  the  images. 

So  far  as  possible  the  various  tests  which  were  suggested  for 
heterophoria  should  be  called  into  requisition  in  heterotropia. 

In  the  class  of  cases  which  will  be  considered  farther  on  and 
which  are  known  as  anotropia  or  katotropia,  the  images  may  vary 


376  ANOMALIES  OF  MOTOR  MUSCLES. 

materially  in  their  deviation,  according  to  the  eye  which  is  used  for 
fixation. 

In  a  case  of  anotropia,  for  example,,  if  a  red  glass  is  placed  before 
the  left  eye,  the  right  eye  may  and  (in  cases  where  there  is  no  great 
difference  in  refraction  or  visual  power  and  in  which  there  is  no  great 
lateral  deviation  of  one  eye)  usually  does  become  the  fixing  eye. 
In  this  case  the  left  eye,  that  covered  by  the  red  glass,  may  deviate 
above  the  other;  but  if  the  red  glass  is  changed  and  the  left  eye 
becomes  the  fixing  eye,  the  right  eye  then  deviates  above  the  other. 
Thus  there  may  be  right  or  left  hypertropia,  depending  upon  the 
eye  which  is  in  fixation. 

The  examination  of  the  various  rotations  by  the  tropometer  will 
generally  bring  to  light  facts  of  the  greatest  importance,  not  only  in 
regard  to  the  nature  of  the  deviations,  but  to  their  aetiology. 

In  converging  strabismus  it  is  generally  the  case  that  the  nasal 
rotations  are  rather  excessive  and  that  the  temporal  rotations  are 
rather  less  than  usual.  They  are  usually  very  nearly  or  quite  equal 
for  the  two  eyes.  But  it  is  in  the  vertical  rotations  that  the  most 
notable  departure  from  the  ordinary  standards  is  found.  In  some 
of  the  cases  of  converging  strabismus  the  rotations  of  both  eyes  in 
the  upward  direction  are  astonishingly  great,  and  in  nearly  all  cases 
they  are  unequal.  It  is  not  unusual  to  see  the  eyes  of  a  squinter  with 
converging  displacement  rotate  one  of  the  eyes  as  high  as  50°  or  52° 
of  arc,  or  nearly  20°  above  the  highest  rotation  in  the  best  adjust- 
ments. In  other  cases,  much  more  rare,  the  upward  rotation  is  ex- 
tremely restricted.  These  later  cases  are  much  more  rare  in  con- 
verging than  in  diverging  squint. 

In  the  case  of  the  extravagantly  high  rotations  there  is  generally 
a  corresponding  failure  to  rotate  downward,  although,  where  there 
is  a  considerable  difference  in  the  degree  of  upward  rotation  of  the 
two  eyes,  there  is  sometimes  a  disproportionate  rotation  down,  so 
that,  with  a  rotation  up  of  50°  or  an  excess  of  more  than  15°,  there 
may  be  a  rotation  down  of  40°  or  a  deficiency  of  only  10°. 

The  stereoscope  has  been  largely  employed,  or  at  least  recom- 
mended, for  the  purpose  of  ascertaining  the  ability  to  see  singly.  It 
has,  however,  when  used,  been  employed  principally  to  prove  the  pres- 
ence of  single  vision  after  squint  operations. 

That  a  mildly  strabismic  subject  should  at  a  near  point  be  able, 
when  using  24°  of  prism  (the  usual  strength  of  the  prisms  of  the 
Brewster  stereoscope)  and  a  magnifying  glass,  to  combine,  or  think 


VAKIOUS  TESTS.  377 

that  he  combines,  momentarily.,  the  figures  on  the  stereoscopic  card 
is  no  proof,  indeed  no  suggestion  that  he  sees  singly  except  under  such 
abnormal  circumstances.  Even  cases  in  the  category  characterized 
by  von  Graefe  as  cases  of  "incompatibility  to  single  vision/'  may  unite 
these  figures.  , 

As  a  matter  of  fact,  while  the  stereoscope  is  an  instrument  of 
value  in  certain  experiments  of  physiological  optics,  it  has  absolutely 
no  value  in  the  determination  of  the  question  of  habitual  binocular 
vision  or  habitual  diplopia. 

A  test  sometimes  employed  for  the  determination  of  the  pres- 
ence or  absence  of  binocular  vision  is  that  of  Hering,  which  is  based 
upon  the  principle  that  the  visual  perception  of  depth  depends  upon 
binocular  vision,  and  that  without  it  the  comparative  distance  of 
objects  can  only  be  judged  by  their  surroundings.  This  test  is  the 
experiment  with  falling  bodies.  If  a  person  having  binocular  vision 
looks  through  a  long  tube,  fixing  the  gaze  upon  a  slender  thread 
stretched  in  front  of  it,  and  if  then  little  balls,  glass  beads,  and  like 
objects  are  let  fall  now  beyond  the  thread  and  now  nearer  the  tube 
than  the  thread,  the  person  experimented  with  will  instantly  detect 
whether  the  body  falls  in  front  of  the  thread  or  behind  it.  If,  on  the 
other  hand,  the  person  examined  has  not  binocular  vision  he  can  only 
tell  by  accident  whether  the  ball  falls  less  or  more  remote  than  the 
thread. 

While  the  principle  upon  which  this  test  is  based  is  in  general 
correct,  it  is  not  by  any  means  always  so,  and  it  is  far  from  being  a 
practical  test  of  binocular  vision. 

The  perimeter  has  also  been  suggested  as  a  means  of  measuring 
the  deviations  of  squint.  The  method  of  its  use  will  be  described 
under  the  discussion  of  paralytic  strabismus.  As  a  means  of  deter- 
mining the  deviations  of  concomitant  strabismus  it  has  little  if  any 
value. 

When  all  the  tests  of  diplopia  and  the  relative  displacements  of 
the  images  have  been  made  at  a  distance  it  is  well  to  make  somewhat 
similar  tests  for  binocular  vision  or  for  the  deviation  of  the  optic 
axes  at  near  points.  The  tests  for  deviation  in  exclusion  and  for 
diplopia  already  mentioned  have  been  supposed  to  be  made  at  the 
distance  of  not  less  than  twenty  feet.  For  near  tests  the  distance 
may  be  selected  according  to  circumstances  within  the  range  of  from 
a  few  inches  to  one  or  two  feet  in  advance  of  the  eyes.  These  tests 
at  near  points  should  always  be  regarded  simply  as  checks  upon  the 


378  ANOMALIES  OF  MOTOR  MUSCLES. 

tests  at  a  distance.  They  may  call  attention  to  certain  conditions 
which  might  otherwise  be  overlooked.  Tests  at  near  points  should 
never  be  made  the  basis  of  treatment,  nor  are  such  tests  to  be  taken 
into  consideration  as  indicating  directly  the  displacements  of  the 
visual  lines. 

After  the  patient  has  been  trained  in  the  recognition  of  diplopia, 
a  bright  point — for  instance,  a  small  opening  in  a  dark-colored  card 
which  is  held  between  the  eyes  of  the  patient  and  a  strong  light — will 
in  general  serve  the  purpose  of  a  test  object  at  a  near  point. 


SECTION-  XLA7. 

The  specific  divisions  of  heterotropia  are: — 

1.  Esotropia. — A  deviation  of  the  visual  lines  inward. 

2.  Exotropia. — A  deviation  of  the  visual  lines  outward. 

3.  Ilypertropia. — A  deviation  of  one  of  the  visual  lines  above 
the  other. 

The  term  hypertropia  does  not  imply  that  the  visual  line  which 
rises  above  the  other  is  too  high.  Both  may  be  too  low. 

The  excess  of  upward  or  downward  direction  of  the  visual  lines 
is  designated  by  other  terms. 

4.  Hyperesotropia  and  hyperexotropia  are  compound  terms  ap- 
plied to  the  conditions  in  which  lateral  and  vertical  deviations  are 
combined. 

ESOTROPIA. 

That  form  of  strabismus  which  is  principally  characterized  by 
excessive  convergence  of  the  eyes  is,  to  appearances,  by  far  the  most 
common.  When,  however,  the  less  conspicuous  cases  of  exophoria 
are  taken  into  consideration  the  proportion  of  each  is  about  the  same. 

It  commences  in  the  great  majority  of  cases  in  the  early  period 
of  childhood.  It  is  first  observed  by  the  parents  of  the  child  at  an 
age  varying  from  two  years  to  six  years.  Although  in  a  less  number 
of  cases  there  is  observed  periodical  squint,  which  is  probably  more 
than  the  usual  vague  infantile  wandering  of  the  eyes,  even  during 
the  first  year. 

In  many  of  the  cases  the  mother  associates  the  origin  of  the 
squint  with  some  critical  event,  such  as  an  infantile  disease;  mea- 
sles and  whooping-cough  being  the  troubles  to  which  the  defect  is 


ESOTROPIA.  379 

most  commonly  attributed.     Accidents,  such  as   falling   downstairs, 
a  slight  blow  about  the  head,  and  fright  are  often  assigned  as  causes. 

In  general,  the  deviation  is  at  first  only  periodical,  occurring 
especially  when  the  child's  attention  is  specially  exerted  or  when  look- 
ing to  one  side.  After  its  first  appearance  it  sometimes  disappears  to 
return  again  after  a  few  days  or  weeks.  At  length  the  defect  seems 
to  settle  in  one  eye.  If  the  eyes  are  unlike  in  refraction  the  eye  most 
nearly  emmetropic  may  remain  the  fixing  eye.  If  there  is  a  high 
degree  of  declination,  especially  a  negative  declination  of  one  eye 
and  a  moderate  declination  of  the  other,  it  is  likely  to  be  the  eye 
with  least  declination  that  habitually  fixes;  or  if  one  eye  is  nearly 
emmetropic,  the  other  myopic,  the  emmetropic  or  slightly  hyperopic 
eye  may  be  emploj'ed  for  fixation  at  a  distance,  while  the  myopic  eye 
may  be  used  for  fixing  at  near  points,  as  in  reading. 

If  one  eye  habitually  deviates,  that  eye  loses  to  a  greater  or  less 
extent  its  keenness  of  visual  sense.  It  becomes  progressively  more 
and  more  amblyopic  in  nearly  all  cases,  the  loss  of  visual  acuity 
extending  to  such  a  degree  in  some  instances  that  the  forms  of  objects 
are  not  made  out.  The  condition  is  generally  known  in  ophthalmic 
literature  under  the  designation  of  amblyopia  ex  anopsia. 

A  converging  strabismus  for  distance  may  become  a  divergent 
squint  when  the  object  seen  is  at  the  distance  of  reading,  a  fact  of 
great  importance  when  the  causes  of  the  deviations  are  under  con- 
sideration. 

A  subject  of  slight  esotropia  who  is  not  myopic  will  sometimes 
hold  the  book  or  the  article  upon  which  he  works  quite  near  to  the 
eyes  in  order  to  take  advantage  of  the  crossing  of  the  visual  lines  at 
the  near  point,  preferring  to  exercise  the  accommodation  to  an  ex- 
treme degree  rather  than  suffer  the  confusion  of  the  double  images 
which  results  if  the  work  is  held  at  the  usual  distance.  This  pecul- 
iarity I  have  found  in  a  few  persons  who,  as  the  result  of  hyperphoria, 
squint  in  at  near  points  only,  and  who,  although  normally  hyperopic 
to  a  high  degree  and  also  presbyopic,  are  accustomed  to  bring  the 
paper  which  they  wish  to  examine,  as,  for  example,  a  check  or  a 
short  note,  close  to  the  eyes  to  read  it.  Two  of  these  persons,  one  of 
whom  is  a  physician,  have  normal  hypermetropia  of  3.00  D  and  each 
is  over  60  years  of  age.  With  one  eye  only  neither  of  these  people 
sees  at  near  points  differently  from  others  with  similar  refraction 
and  presbyopia. 

The  power  of  the  lateral  excursions  of  the  two  eyes  in  converg- 


380 


ANOMALIES  OF  MOTOR  MUSCLES. 


ing  strabismus  is  very  nearly  uniform  for  each  direction.  In  many 
cases  the  nasal  rotation  is  considerably  increased,  so  that  the  border 
of  the  cornea  is  carried  well  into  the  inner  canthus  or  is  even  buried 
behind  the  caruncle. 

On  the  other  hand  the  temporal  rotations  are  often  reduced  in 
about  the  same  proportion.  Measured  by  the  tropometer  the  nasal 
rotation  ranges  from  55°  to  00°  or  65°,  while  the  nasal  rotation  in 
well-balanced  eyes  is  found  to  be  about  50°. 

To  the  temporal  side  the  rotations  are  about  35°  to  40°,  which 
is  less  than  in  well-balanced  eyes. 

The  upward  rotations  in  esotropia  are,  in  a  very  large  propor- 
tion of  cases,  extreme,  ranging  from  50°  to  55°  while  the  normal 


Fig.  147.  Fig.  148.  Fig.  149. 

Two  Cases  of  Convergent  Strabismus  and  One  of  Paralysis. 

rotation  up  is  33°,  or  a  little  more.  The  downward  rotation  is  re- 
stricted, but  to  a  less  extent  than  the  upward  is  increased.  And  the 
upward  rotations  are  generally  nearly  equal. 

Esotropia,  although  in  appearance  a  direct  turning  in  of  the 
deviating  eye,  is  rarely  a  simple  condition.  There  is  nearly  always 
a  certain  extent  of  deviation  of  one  of  the  eyes  in  the  vertical  direc- 
tion. As  it  will  be  seen  when  the  aetiology  of  strabismus  is  under 
consideration,  there  is,  in  fact,  always  a  maladjustment  of  one  or 
both  eyes  in  the  vertical  direction  in  converging  strabismus,  but  it  is 
the  purpose  here  to  call  attention  only  to  the  inequality  of  vertical 
tensions  of  the  directing  muscles  which  is  very  common  in  all  lateral 
forms  of  squints. 


ESOTHOP1A.  381 

If  the  patient  is  able  to  locate  the  double  images  it  will  gener- 
ally be  easy  to  detect  the  difference  in  height  of  the  images  when  a 
red  glass  is  placed  in  front  of  one  eye.  In  esotropia  the  cliplopia 
is,  according  to  the  rule,  homonymous,  and  the  prism,  with  its  base 
out,  which  either  brings  one  of  the  images  directly  in  the  vertical 
line  with  the  other  or  which  unites  the  images,  is  the  measure  of  the 
deflection — the  degree  of  esotropia.  If  hypertropia  is  associated  with 
esotropia,  as  it  usually  is,  the  prism  with  its  base  down  before  the 
eye,  with  the  lower  image,  completes  the  measure  of  the  two  elements 
of  the  deflection. 

As  it  has  been  said  in  the  discussion  of  the  general  conditions  of 
strabismus  (page  365),  there  are  exceptions  to  the  rule  that  the 
images  are  homonymous  in  esotropia.  The  exceptions  are  rare  and 
are  always  associated  with  hypertropia.  Instances  of  this  unusual 
position  of  the  double  images  will  be  mentioned  in  the  section  on 
"Exotropia." 

By  the  tests  of  deviation  in  exclusion  this  oblique  direction  of 
the  deviation  can  be  observed  if  sufficient  care  is  exercised  in  the 
examination. 

The  axes  of  the  two  eyes  do  not,  in  esotropia,  always  maintain 
the  same  relative  positions;  for  while  within  a  certain  range  the 
deviating  eye  will  deviate  in  more  and  more  in  proportion  as  the 
object  is  brought  nearer  the  eyes  and  the  fixing  eye  becomes  more 
convergent,  within  that  range  the  relative  convergence  may  become 
more  nearly  equal  and  the  squinting  consequently  less,  until,  as 
has  been  already  stated,  in  certain  cases  the  visual  lines  may  meet 
at  the  object.  In  the  more  extreme  cases  the  deviation  of  the  strabis- 
mic  eye  continues,  that  eye  deviating  in  more  and  more  as  the  object 
approaches  the  visual  lines  crossing  between  the  eyes  and  the  object 
as  long  as  the  fixing  eye  continues  to  converge. 

In  other  cases  this  same  deviation  when  the  convergence  of  the 
fixing  eye  reaches  a  certain  extent  becomes  suddenly  even  much  more 
extreme  than  before,  and  the  deviating  eye  appears  to  be  drawn  spas- 
modically into  the  inner  canthus.  In  still  other  cases,  when  the  con- 
vergence of  the  fixing  eye  has  reached  a  certain  stage  the  deviating 
eye*  suddenly  turns  out,  and  diverging  strabismus  results. 

Converging  strabismus  is  more  frequently  associated  with  hyper- 
metropia  than  with  other  refractive  states  of  the  eyes.  This  fact  has 
led  to  the  supposition  that  the  refractive  state  of  hypermetropia  is 
causative  of  the  squint.  This  subject  will  receive  attention  in  a 


382  ANOMALIES  OF  MOTOR  MUSCLES. 

special  section  and  need  be  referred  to  here  only  as  one  of  the  phe- 
nomena often  attending  this  form  of  strabismus.  But  the  refractive 
conditions  attending  converging  strabismus  arc  various,  being  in 
some  cases  emmetropia,  in  other  cases  astigmatism,  in  a  considerable 
number  hyperopia,  and  in  a  less  number  myopia. 

Subjects  of  converging  strabismus  are  usually  fatigued  from 
slight  causes.  They  have,  in  general,  little  physical  endurance,  and 
are,  more  than  the  average  persons,  subject  to  various  illnesses  which 
may  happen  to  prevail.  Hence  the  proportion  of  persons  with  con- 
verging strabismus  who  reach  adult  age  is  less,  independent  of  the 
results  of  operations,  than  it  is  among  other  children.  They  have,  as 
a  rule,  much  headache,  the  pain  of  which  is  experienced  especially  in 
the  forehead  and  temples.  Women  with  converging  squint  are  apt 
to  be  hysterical  and  men  are  likely  to  be  nervous  and  often  morose. 
Dyspepsia,  despondency,  and  eccentricity  are  rather  characteristic 
associated  conditions.  Xeuralgia  about  the  temples  and  face  and 
pains  in  the  dorsal  region  are  also  common  symptoms  with  converg- 
ing strabismus.  The  subjects  of  the  defect  often  start  out  well  in 
the  morning,  but  become  nervously  exhausted  before  night. 

They  are  also  subject,  to  an  extent  greater  than  the  average 
persons,  to  chronic  diseases  of  various  organs,  as,  for  example,  the 
lungs  or  kidneys.  When  Bright's  disease  exists  associated  with  con- 
verging strabismus,  paresis  of  the  externi  with  diplopia  becomes  one 
of  the  frequent  complications. 

EXOTROPIA — DIVERGING  STRABISMUS. 

In  exotropia  or  diverging  strabismus  the  defect  is  usually  very 
plain  to  be  seen  and  constitutes  a  feature  of  facial  expression  more 
striking  than  a  deviation  of  equal  extent  in  the  opposite  direction. 
If  the  usually  fixing  eye  in  exotropia  is  covered,  the  deviating  eye 
moves  from  the  temporal  direction  inward  in  order  to  place  itself 
in  fixation,  and  the  previously  fixing  eye  moves  outward  toward  the 
temple  to  an  extent  equal  to  the  moving  in  of  the  usually  deviating 
eye. 

If  the  subject  of  the  strabismus  is  able  to  recognize  diplopia,  a 
red  glass  before  the  right  eye  will  show  a  red  image  at  the  left  of 
the  image  of  the  left  eye,  and  if  the  colored  glass  is  placed  before 
the  left  eye  the  red  image  is  seen  at  the  right  of  the  other.  If  a 
change  in  the  vertical  relations  of  the  images  is  required  in  order 
to  obtain  the  notion  of  diplopia,  a  change  such  as  may  be  made  by 


EXOTROPIA.  383 

the  phorometer  or  by  a  prism  with  its  base  up  or  down  before  one 
eye,  the  image  seen  by  the  right  eye  will  appear  at  the  left  of  that 
seen  by  the  left  eye. 

The  defect  is  rarely  observed  during  the  first  two  or  three  years 
of  life,  and  frequently  not  before  the  eighth  or  tenth  year. 

It  is  less  frequently  periodical  than  the  converging  form  of 
squint,  and  rarely,  after  being  once  established,  disappears,  as  does 
the  form  of  esotropia. 

The  very  general  belief  that  divergent  strabismus  is  usually  asso- 
ciated with  myopia  does  not  appear  to  be  borne  out  by  a  long  series 
of  examinations  carefully  made,  and  while  myopia  prevails  to  a 
greater  degree  in  diverging  squint  than  in  the  converging  form,  the 
two  conditions  cannot  be  said  to  be  generally  associated.  According 
to  my  own  records  myopia  is  found  in  about  25  per  cent,  of  cases  of 


_ 


Fig.  150.  Fiff.  151. 


Indicating  the  Compound  Direction  of  the  Deviating  Eye 
in  Diverging  Strabismus. 

exotropia  with  or  without  hypertropia,  which  is  about  the  per  cent, 
of  emmetropia,  while  hypermetropia  has  been  found  in  very  nearly 
50  per  cent,  of  all  my  cases  of  exotropia.  (See  table,  page  409.) 

If  the  deviation  of  esotropia,  converging  strabismus,  is  often 
associated  with  hypertropia,  even  more  pronounced  is  the  association 
of  exotropia  with  the  deviation  in  the  vertical  direction.  It  is  in- 
deed rare  to  find  the  images  in  the  crossed  diplopia  of  divergent 
strabismus  in  the  same  plane,  and  the  degree  of  hypertropia  is  usu- 
ally considerable. 

As  in  converging  strabismus  there  is  often  a  somewhat  increased 
medial  rotation  of  both  eyes,  so  there  is  with  diverging  squint  fre- 
quently a  moderate  restriction  of  the  nasal  with  a  somewhat  increased 
temporal  rotation.  The  extent  of  the  restriction  of  the  nasal  and  of 
the  increase  of  the  temporal  rotations  do  not,  however,  bear  any 
proportionate  relation  to  the  extent  of  divergence,  and  the  extent  of 


384  ANOMALIES  OF  MOTOR  MUSCLES. 

inward  rotation  is  generally  about  equal  for  the  two  eyes.  This  rule 
does  not  hold  good  when  with  a  eonsiderable  degree  of  hypertropia 
one  eye  is  adjusted  nearly  in  what,  for  convenience,  may  be  called 
the  normal  plane.  In  that  ease  the  eye  which  is  adjusted  for  a  plane 
neither  too  high  nor  too  low  will  have  a  greater  freedom  of  rotation 
in  the  nasal  direction  than  its  fellow,  which  will  be  held  back  by  the 
action  of  the  vertically  acting  muscles. 

With  such  exceptions,  which  are  of  a  purely  mechanical  nature 
and  always  depending  on  the  vertically  acting  muscles  or  the  char- 
acter of  the  declination,  the  nasal  rotations  in  diverging  strabismus 
are  equal  and  usually  sufficient. 

That  in  exotropia,  the  function  of  associated  convergence  of  the 
two  eyes  is  insufficiently  performed  is  too  evident.  Indeed,  this  in- 
sufficiency of  the  converging  function  is  the  conspicuous  symptom 
of  this  form  of  strabismus.  Such  failure  in  this  function  is  not  asso- 
ciated Avith  an  actual  absence  of  the  ordinary  power  of  moving  each 
eye  to  the  nasal  side  Avhen  acting  alone.  This  may  be  shoAvn  either 
by  the  use  of  the  tropometer,  in  which  case  the  degree  of  rotations  can 
be  accurately  established,  or  by  causing  the  exotropic  persons  to 
move  the  eyes  from  side  to  side  Avhile  the  observer  notes  the  extent 
of  movements  both  out  and  in. 

Exotropic  persons  are,  much  more  than  esotropic  subjects,  accus- 
tomed to  close  one  eye  Avhen  reading  or  Avorking.  They  are  often 
subject  to  constant  dull  pains  about  the  eyes  and  to  dizziness.  They 
generally  have  frequent  and  severe  headaches  and  pains  in  the  back 
of  the  head  and  neck.  Pains  in  this  locality  are  more  characteristic 
than  those  in  the  forehead  so  common  with  esotropia.  There  is  often 
confusion  of  ideas  and  mental  exhaustion. 

HYPERTROPIA — STRABISMUS  SURSUMVERGENS. 

This  form  of  strabismus  which  has  been  regarded  as  rare  is,  in 
fact,  the  most  common  of  all  the  forms.  Not  only  does  it  constitute 
a  very  considerable  proportion  of  the  cases  of  squint  in  Avhich  it  is 
either  the  only  or  the  most  conspicuous  element  of  the  defect,  but  it 
is  associated  Avith  a  great  proportion  of  the  two  forms  which  have 
received  from  authorities  on  the  subject  almost  exclusiA~e  attention. 

A  deviation  of  one  eye  above  or  beloAV  its  fellow,  unless  to  an 
extravagant  extent,  is  so  much  less  than  a  lateral  deviation  notice- 
able that  the  friends  of  patients  and  patients  themselves  are  fre- 
quently not  aAvare  of  the  defect,  and  those  who  haAre  examined  squint 


HYPERTROPiA.  385 

from  the  point  of  view  of  cosmetics  have  overlooked  a  great  many 
cases  belonging  to  this  cla?s  while  carefully  recording  those  in  which 
moderate  converging  or  diverging  deviations  have  appeared.  That 
during  the  last  few  years,  especially  in  America,  these  cases  have  been 
more  frequently  recognized  than  previously,  is  clearly  to  be  seen  by 
the  literature.  Yet  the  fact  remains  that  even  now  and  in  America 
many  cases  of  hypertropia  appear  to  fail  of  recognition. 

One  may  be  subject  to  a  degree  of  vertical  squint  which  is  suf- 
ficient to  prevent  the  possibility  of  binocular  single  vision  and  to 
result  in  a  high  degree  of  amblyopia  while  the  defect  does  not  attract 
much  attention.  The  fact  that  the  individual  has  not  an  agreeable 
expression  of  the  eyes  is  regarded  simply  as  a  personal  peculiarity 
which  is  not  clearly  classified.  The  defect  shows  mostly  when  the 
subject  of  it  is  looking  at  a  considerable  distance,  but  in  many  cases 
it  manifests  itself  by  an  inward  or  outward  squint  when  the  hyper- 
tropic  person  looks  at  a  near  point,  as  in  reading.  This  inward  or 
outward  deviation  at  near  points  has  been  supposed  to  arise  from 
some  disturbance  between  the  function  of  accommodation  and  that 
of  convergence,  and  has  been  ascribed  to  hypermetropia.  We  have 
here  to  call  attention,  not  to  the  cause,  but  to  the  phenomenon,  and 
this  is  an  important  phenomenon,  which  has  been  absolutely  ignored 
by  all  the  writers  on  the  subject  of  squint.  In  all  cases  in  which  a 
converging  squint,  not  observable  when  the  patient  looks  at  a  dis- 
tance, occurs  when  he  looks  at  a  near  object,  either  an  actual  vertical 
squint  or  at  least  a  high  degree  of  hyperphoria  exists. 

The  ease  with  which  vertical  squint  of  a  high  degree  may  escape 
attention  is  illustrated  in  the  following  case: — 

C.  F.,  age  40,  is  a  gentleman  of  means  and  education  who  has  lived  a 
life  of  leisure,  but  has  been  all  his  life  a  valetudinarian.  Application  to  any 
employment  which  has  demanded  the  concentration  of  vision  at  any  one  point 
for  a  considerable  time  has  been  always  distasteful  to  him,  and  although  a 
man  of  much  general  culture  he  has  never  been  a  reader.  He  has  known  since 
boyhood  that  one  of  his  eyes  was  much  "stronger"  than  the  other  and  he  has 
since  his  early  boyhood  been  subject  to  frequent  and  severe  attacks  of  head- 
aches. He  has  consulted  many  physicians  on  account  of  his  nervous  troubles 
and,  as  his  eyes  have  annoyed  him,  he  has  seen  a  number  of  distinguished 
oculists,  who  have  prescribed  glasses,  some  of  which  he  has  with  him  at 
present. 

The  vision  of  the  right  eye  is  8/o  and  of  the  left  e/15,  and  no  glass  im- 
proves the  sight  of  either  eye  at  6  meters.  There  is  no  indication  of  disease  of 
either  eye.  He  has  never  been  told  that  he  has  strabismus,  and  his  wife,  a 
very  intelligent  lady,  is  astonished  to  hear  that  he  is  strabismic. 


ANOMALIES  OF  MOTOR  MUSCLES. 

When  the  patient  is  directed  to  look  at  the  flame  of  a  candle  on  the  oppo- 
site side  of  the  room,  if  a  visiting  card  is  slipped  in  front  of  the  right  eye,  the 
candle  is  not  seen  for  a  second  or  two,  but  the  left  eye  can  be  seen  to  turn 
from  below  upward  until  it  has  the  candle  in  fixation.  If  a  prism  of  from.  12° 
to  15°  with  its  base  down  is  placed  before  the  right  eye  so  that  in  the  first 
fixation  the  right  eye  is  obliged  to  look  up  to  that  extent,  but  little  movement 
can  be  detected  on  the  part  of  the  left  eye  when  the  right  is  excluded.  It  was 
at  the  first  and  second  examinations  impossible  for  him  to  recognize  diplopia 
without  aid  or  by  the  help  of  colored  glasses  and  prisms  or  by  any  device. 

By  the  table  on  page  409  it  will  be  seen  that  hypertropia  occurs 
as  the  principal  element  of  squint  in  24y2  per  cent,  of  all  the  cases 
of  strabismus,  and  that  it  is  an  important  element  in  more  than  50 
per  cent.,  while  it  is  also  present  in  nearly  all,  if  not  all,  cases  of 
concomitant  squint. 

In  the  cases  included  in  the  table  it  does  not  follow  that  there 
is  always  an  absence  of  hypertropia  where  it  is  not  recorded,  for  in 
some  cases  the  difficulty  of  obtaining  exact  information  respecting 
the  relative  positions  of  images  is  so  great  that  such  an  element  may, 
even  where  care  is  exercised,  not  be  revealed. 

The  disabilities  of  the  eyes  and  the  general  neurasthenic  symp- 
toms which  are  commonly  associated  with  esotropia  are  also  fre- 
quently found  with  hypertropia.  Thus,  headache  is  one  of  the  most 
common  of  the  associated  symptoms.  In  the  case  of  simple  hyper- 
tropia, however,  the  pain  is  often  located  in  the  upper  part  of  the 
forehead  or  even  back  of  this  over  the  eye,  the  visual  line  of  which 
is  directed  lowest  and  directly  over  the  brow  of  the  eye  deviating 
upward.  While  this  is  so  frequently  the  case  as  to  be  characteristic, 
it  is  not  always  so,  and  there  are  cases  with  hypertropia  who  rarely 
if  ever  have  headache. 

In  many  cases  the  headache  is  of  the  character  of  migraine  with 
vomiting  or  excessive  nausea.  Dizziness  is  very  common  with  hyper- 
tropia, and  the  cases  in  which  vertigo  is  a  prominent  symptom  are  so 
common  that  vertigo  may  be  regarded  as  a  characteristic  symptom 
with  vertical  squint.  In  moderate  cases  the  patient  is  able  to  unite 
the  images  of  the  two  eyes  when  looking  at  points  quite  near  to  the 
eyes,  and  not  unfrequently  it  will  be  observed  that  such  patients  hold 
their  book  or  their  work  very  close  to  the  eyes,  suggesting  a  high 
degree  of  myopia,  although  an  actual  hypermetropia  may  exist.  In 
such  cases  the  greater  effort  at  adjustment  is  preferred  to  the  con- 
fusion of  diplopia. 


HYPERTROPIA.  387 

Excessive  laclirymation  is  also  a  frequent  associated  condition 
with  vertical  strabismus,  as  it  is  also  with  decided  hyperphoria. 

Mental  confusion  occurs  in  a  very  considerable  percentage  of 
cases. 

Amblyopia  of  the  squinting  eye  is  even  much  more  pronounced 
than  in  converging  squint,  and  it  may  be  said  that  in  this  latter 
form  of  strabismus  the  extent  of  amblyopia  is  largely  in  proportion 
to  the  degree  of  hypertropia  which  exists  as  an  element  in  the  case. 

In  many  cases  of  hypertropia  with  moderate  lateral  deviation  it 
is  quite  impossible  for  the  patient  to  locate  the  light  from  the  flame  of 
a  candle  in  any  part  of  the  field  of  vision.  Hence,  the  eye  cannot  by 
any  effort  of  the  will  be  directed  toward  a  given  object.  In  cases  in 
which  conscious  diplopia  can  be  induced,  the  latter  is  sometimes 
homonymous  for  distant  objects  and  crossed  for  near;  in  other  cases 
the  diplopia  remains  homonymous  for  a  length  of  time,  perhaps  for 
years,  then  changes  to  crossed  diplopia.  Such  a  case  may  remain  for 
years  as  a  converging  strabismus,  and  at  a  later  period  become  a  pro- 
nounced diverging  squint.  Such  cases  belong  to  the  class  of  sponta- 
neous cures  or  cures  from  convex  glasses.  The  convergence  or  di- 
vergence in  these  cases  represents  only  the  swing  inward  and  outward 
of  an  eye  held  suspended  above  or  below  its  fellow. 

In  a  proportion  of  these  cases  there  is  also  an  apparent  contra- 
diction in  the  indications  from  diplopia  and  from  the  apparent  devia- 
tions and  the  deviations  in  exclusion.  The  apparent  deviation  may 
be  convergent,  the  eyes  appearing  crossed,  but  if  a  card  is  slipped 
alternately  before  one  and  then  the  other  eye  each  eye  will  be  seen 
to  move  distinctly  in  toward  the  nose  when  changing  from  exclusion 
to  fixation,  thus  showing  that  the  excluded  eye  drifted,  not  in,  but 
out  in  exclusion.  Again,  the  appearance  may  be  that  of  divergent 
squint  and  the  deviation  may  correspond  with  this  appearance,  yet 
the  double  images  may  be  homonymous.  These  and  some  other  seem- 
ingly contradictory  phenomena  are  the  result  of  high  degrees  of 
declination  which  attend  these  cases  of  hypertropia. 

In  cases  of  comparatively  simple  hypertropia  the  diagnosis  is 
easy,  since  even  when  double  images  are  not  recognized,  the  test  of 
deviation  in  exclusion  quickly  reveals  the  defect. 


388  ANOMALIES  OF  MOTOR  MUSCLES. 


SECTION  XLIX. 

ANOTROPIA  AND  KATOTROPIA— THE  TWO  FORMS  OF  DOUBLE 
VERTICAL  STRABISMUS.1 

These  more  or  less  symmetrical  forms  of  deviation  of  the  two 
e}Tes  vertically,  either  up  or  down,  and  those  comparatively  sym- 
metrical unfavorable  adjustments  in  the  vertical  direction  which  are 
of  less  extent  than  strabismus,  were  not  recognized  by  former  writers. 
Attention  was  called  to  them  by  myself  at  the  meeting  of  the  British 
Medical  Association2  held  in  Bristol  in  1894,  and  at  the  International 
Ophthalmological  Congress  at  Edinburgh3  of  the  same  year. 

There  is  a  clearly  dividing  line  between  the  strabismic  forms 
of  deviations  of  this  type  and  the  forms  which  I  have  called  ano- 
phoria  and  katophoria.  In  the  more  extreme  form  the  two  eyes  may 
be  seen  alternately  to  deviate  vertically  and  in  the  same  direction 
when  a  screen  is  passed  from  before  one  to  the  other  and  back  again. 

Notwithstanding  the  fact  that  these  are  the  least  conspicuous 
forms  of  strabismus,  they  are  so  far  from  being  of  the  least  impor- 
tance that  they  may  be  regarded  as  ranking  before  all  other  forms 
as  of  paramount  significance. 

A  careful  consideration  of  these  deviations  is  of  primary  moment 
in  the  study  of  converging  and  diverging  strabismus. 

These  double  vertical  deviations  are  not  to  be  regarded  as  being 
the  same  conditions  as  those  formerly  known  and  described  in  the 
text-books  as  strabismus  sursumvergens  •  or  strabismus  deorsumvergens, 
for  in  these  later  conditions  one  eye  is  supposed  to  be  correctly  ad- 
justed in  respect  to  the  horizon,  while  the  other  eye  deviates  above 
or  below  this  well-adjusted  eye.  Such  conditions  are  in  this  work 
described  under  the  terms  hypertropia,  right  or  left.  As  a  matter 
of  fact  many  cases  which  have  been  regarded  as  simple  hypertropia, 
strabismus  sursum-  or  deorsumvergens,  in  reality  belong  to  the  class 
now  under  consideration,  and  the  choice  of  one  eye  to  be  used  in 
fixation  while  the  other  is  permitted  to  deviate  above  it  or  below  it  is 


'For  the  conditions  of  symmetrical  forms  of  vertically  deviating  tenden- 
cies of  degrees  less  than  strabismus,  see  page  217. 

2  "On  Double  Vertical  Strabismus,"  a  paper  read  before  the  Section  of 
Ophthalmology  of  the  British  Association,  July,  1894,  and  published  in  Annales 
d'Oculistique,  April-June.  1895. 

8  "Transactions  of  the  Eighth  International  Ophthalmological  Congress,'* 
page  226. 


DOUBLE   VERTICAL   STRABISMUS.  389 

similar  to  the  condition  in  converging  strabismus  where  one  eve  is 
selected   for   habitual    fixation,    although   there   may   be   as   great    a 
tendency  toward  deviation  in  one  as  in  the  other  eye. 
The  forms  of  adjustment  in  this  class  are: — 

1.  Anotropia,  a  deviation  of  the  visual  line  of  either  eye  upward 
when  the  other  eye  is  in  fixation. 

2.  Katotropia,  a  deviation  of  the  visual  line  of  either  eye  down- 
ward when  the  other  is  in  fixation. 

The  simplest  form  of  double  vertical  squint,  that  in  which  either 
eye  deviates  directly  upward  or  downward  when  the  other  is  in  fixa- 
tion, has  not,  I  believe,  been  described  previously  to  the  description 
contained  in  my  paper  above  alluded  to.  In  these  cases  the  patient, 
in  most  instances,  selects  one  eye  for  habitual  fixation,  while  the  other 
is  permitted  to  diverge  upward  or  downward.  In  the  first  instance, 
if,  while  the  habitually  fixing  eye  is  directed  toward  an  object,  a  visit- 
ing card  is  slipped  between  the  eye  and  the  object,  the  squinting  eye 
is  seen  to  move  directly  downward,  while  the  eye  behind  the  card  rises 
in  a  direction  as  exactly  vertical  as  that  through  which  the  originally 
squinting  eye  descended,  and  to  an  extent  approximately  equal  to  the 
original  squint.  In  some  of  these  cases  the  patient  is  able  to  exchange 
the  fixation  from  one  eye  to  the  other  at  will.  In  these  cases  the  action 
of  the  two  eyes  is  identical  with  that  which  is  shown  when  the  card 
is  used.  If  the  left  eye,  for  example,  squints  upward,  and  the  patient 
is  directed  to  fix  with  that  eye,  the  observer  can  see  the  eye  move 
directly  downward  while  the  other  rises  as  directly. 

If,  while  the  patient  fixes  a  lighted  candle,  a  red  glass  is  slipped 
before  one  eye,  in  many  cases  conscious  diplopia  results  with,  for 
example,  the  red  image  below.  Changing  the  red  glass  to  the  other 
eye,  the  image  of  that  eye  at  once  becomes  the  lower.  This  is  the 
case  in  anotropia.  In  katotropia  the  red  image  will  in  each  instance 
be  above. 

In  nearly  all  these  cases,  by  close  observation,  the  deviating  eye 
can  be  seen,  as  it  comes  down  to  the  position  of  fixation  when  the 
other  is  covered,  to  come  into  position  with  a  twist.  Sometimes  this 
twist  is  very  conspicuous.  A  better  way  to  observe  this  is,  after  put- 
ting, one  eye  under  the  influence  of  cocaine  (or  even  better,  without 
cocaine),  to  place  one  or  two  very  small  squares  of  black  paper,  one 
on  each  side  of  the  cornea,  but  on  the  conjunctiva,  or  two  minute 
white  points  may  be  placed  on  the  cornea,  the  lower  lid  being  held 
away  from  the  eye.  Then  by  changing  the  card  from  one  side  to  the 


390  ANOMALIES  OF  MOTOR  MUSCLES. 

other  as  this  eye  conies  into  fixation,  the  little  back  or  white  points  are 
seen  to  change  direction,  one  going  up,  the  other  down,  many  degrees. 

It  is  thus  seen  that  with  such  double  vertical  squints  there  is 
also  extreme  declination,  and  it  is  this  feature  which,  unquestionably, 
forms  one  of  the  two  causative  elements  in  the  case,  the  other  being 
the  fact  that  in  anotropia  the  plane  of  vision  is  remarkably  high.1 

The  simple  lowering  of  such  eyes  does  not  correct  the  tendency 
to  squint  up,  but  a  correction  of  declination  does. 

Persons  with  this  double  form  of  strabismus  usually  have  a  sort 
of  uncertain  gaze  with  a  goggled  appearance  of  the  eyes. 

There  is  not,  in  the  more  simple  cases  of  double  vertical  devia- 
tion, the  unpleasant  appearance  characteristic  of  convergence  or  diver- 
gence, for  so  long  as  the  cornea  of  each  eye  does  not  deviate  laterally 
from  its  fellow,  a  very  important  deviation  upward  or  downward 
either  escapes  observation  altogether  or  causes  a  much  less  conspicuous 
defect. 

Even  in  the  least  complicated  cases  there  will  be  a  frequent, 
though  transitory,  cast  of  one  or  other  eye  inward  or  outward,  and 
if  the  patient  becomes  fatigued  the  cast  is  more  persistent.  Visual 
confusion,  vertigo,  headache,  are  among  the  symptoms  commonly 
attending  this  anomaly,  and  epileptic  seizures  and  intellectual  dull- 
ness are  also  among  the  unpleasant  attendants  upon  anotropia  and 
katotropia. 

As  an  illustration  of  the  condition  in  which  there  is  actual 
deviation  of  the  eyes  almost  directly  upward  the  following  case  is 
introduced.  It  should  be  said,  however,  that  this  case  was  examined 
and  treated  before  the  introduction  of  the  tropometer  or  clinoscope, 
a  fact  which  accounts  for  the  absence  of  any  exact  measurements  of 
the  rotations  or  declinations.  It  is,  however,  a  remarkably  conspicu- 
ous case,  and  the  elements  not  recorded  may  be  readily  substituted. 

Miss  E.  M ,  aged  14,  seen  in  July,  1894,  had  been  subject  to  constant 

headache  as  long  as  she  could  remember,  often  accompanied  with  dizziness. 
The  persistent  and  intense  pain  in  the  head  at  length  compelled  her  to  abandon 
school,  yet  even  when  she  was  not  engaged  in  study  there  was  great  distress. 

She  was  found  to  be  a  robust  girl,  with  no  organ  diseased,  and  with  no 
apparent  cause  of  disturbance  except  the  eyes.  Examination  of  these  organs 
shows:  vision  of  right  eye,  Vis?  of  left  eye,  %;  each  with  +  1.50  spherical. 

Excluding  either  eye,  the  other  deviates  directly  up  4  to  G  millimeters, 


1  Since  writing  the  above  paragraph  I  have  been  led  to  doubt  the  state- 
ment that  an  extremely  high  plane  of  vision  is  in  all  cases  an  essential  ele- 
ment. It  certainly  is  found  in  most  cases  of  anotropia. 


DOUBLE   VERTICAL  STRABISMUS. 


391 


but  it  is  the  right  eye  which  generally  deviates,  or,  as  her  friends  state  it, 
"rolls  up  into  her  head,"  while  the  left  eye  is  usually  chosen  for  fixation.  She 
can,  however,  fix  either  eye  at  will;  then  its  fellow  deviates  up.  When  she 
is  fatigued  the  deviating  eye  rolls  further  up  than  when  she  is  fresh.  There  is 
no  indication  of  paresis;  indeed,  there  is  ability  to  rotate  the  eyes  freely  in 
all  directions,  except  that  the  upward  rotation  is  greater  than  the  downward. 

If  a  red  glass  is  placed  before  the  right  eye  and  she  fixes  the  left,  there  is 
vertical  diplopia,  right  hypertropia,  5°  to  12°.  If  the  red  glass  is  changed  to 
the  left  eye  and  she  fixes  the  right  eye,  there  is  left  hypertropia,  3°  to  8°.  In 
both  instances  it  is  easy  to  see  that  only  a  portion  of  the  vertical  distance 
between  the  images  is  measured,  for  the  patient  can  be  seen  to  balance  the 
eyes  up  and  down,  and  it  is  evident  that  to  a  large  extent  the  location  of  the 
images  is  modified  by  these  movements. 

The  deviations  upward  are,  in  fact,  more  than  would  require  a  prism  of 
20°  for  correction,  for,  even  when  such  a  prism  is  placed  with  its  base  down 
before  the  deviating  eye,  and  the  other  eye  is  excluded,  the  deviating  eye  is 
seen  to  move  down  for  fixation.  It  is,  therefore,  impossible,  from  the  state- 
ments of  the  patient,  to  form  a  correct  judgment  of  the  actual  amount  of 
deviation  of  the  images. 


f 


Fig. 


152. — Left    Eye    in    Fixation, 
Right  Deviating  up. 


153. — Right  Eye  in  Fixation, 
Left  Deviating  up. 


In  moving  from  deviation  to  fixation  each  eye  moves  down  almost  in  a 
vertical  line,  and  in  returning  from  fixation  to  deviation  each  moves  directly 

up. 

The  figures  152  and  153  show  the  position  of  the  eyes:     152,  when  the  left 

eye  is  fixed;   and  153,  when  the  right  is  directed  to  the  object. 

After  examinations,  made  on  four  or  five  successive  days,  graduated 
tenotomy  was  done  on  the  superior  rectus  of  the  right  eye,  and  a  week  later 
a  similar  operation  was  done  on  the  left  eye.  These  relaxations  were  found 
to  be  insufficient  to  prevent  the  upward  deviations  of  the  eyes,  and  other  care- 
ful tenotomies  have  been  done  on  each  of  these  superior  recti  since  then. 

The  result  has  been  to  correct  the  deviations  to  the  extent  that  they  can 
only  be  perceived  when  the  observer  passes  a  card  from  one  to  the  other  eye 
and  watches  carefully  for  the  movement.  Each  eye,  under  these  circum- 
stances, may  be  seen  to  move  up  very  slightly  in  exclusion,  but  it  has  been 
thought  best  to  permit  considerable  time  to  elapse  before  resorting  to  attempts 
at  a  more  perfect  correction. 

From  the  first  relaxations  the  pains  in  the  head  became  less  intense  and 


392 


ANOMALIES  OF  MOTOR  MUSCLES. 


very  much  less  constant,  and  the  girl  was  able  to  resume  her  place  in  school; 
she  was  no  longer  di/./y. 

Since  the  above  records  were  made  the  examinations  have  been  aided  by 
the  clinoscope  and  the  tropometer,  and  it  is  found  that  while  the  vertical  rota- 
tions are  nearly  normal  there  exist  enormous  declinations.  Further  treat- 
ment has  been  reserved  since  the  girl  appears  so  well  that  further  operations 
may  wait. 

Figs.  154,  155,  150,  and  157  illustrate  two  cases  reported  by  me  in  Annales 
d'Oculistique,  1895,  in  each  of  which  there  was  marked  converging  strabismus. 
As  there  was  also  double  vertical  strabismus,  anotropia,  relaxations  of  the 
superior  rectus  of  each  eye  was  done  with  the  result  of  relieving  the  converg- 
ence in  each  case. 

The  cases  mentioned  above  indicate  the  methods  which  were  employed 
at  the  time  that  they  were  first  under  observation.  Recent  advances  have 


Fig.  154. 


Fig.  155. 


Fig.  156.  Fig.  157. 

Cases  of  Converging  Strabismus  Depending  on  Vertical  Deviations  and 
after  Treatment  Directed  to  the  Superior  Recti  only. 

placed  the  diagnosis,  the  estimation  of  the  degree  of  vertical  strabismus  and 
its  nature  upon  a  much  more  definite  basis.  It  is  no  longer  necessary  to  rely 
upon  the  subjective  phenomena  as  experienced  by  the  patient,  nor  upon  the 
observation  of  the  surgeon  as  an  eye  passes  from  exclusion  to  fixation. 

The  tropometer  affords  a  means  of  determining  with  accuracy 
the  relation  of  the  adjustment  of  either  eye  in  respect  to  the  plane  of 
the  horizon. 

The  clinoscope,  the  lens  clinoscope,  or  the  rude  method  by  the 
black  or  white  bits  of  paper  placed  on  the  eye,  will  aid  in  determining 


PERIODIC  STRABISMUS.  393 

the  declination,  and  by  these  means  much  more  satisfactory  results 
may  be  expected  than  in  the  cases  mentioned. 

SECTION  L. 

PERIODIC  OR  INTERCURRENT  STRABISMUS. 

The  class  of  cases  included  in  this  category  is  made  up  from  the 
classes  already  described.  It  is  a  class  in  which  the  strabismic 
deviation  is  not  constant,  yet  appears  under  certain  circumstances, 
and  is  perhaps  at  times  quite  noticeable.  Yon  Graefe,  in  his  elaborate 
treatise  (Arch,  fur  Oplitlial.,  Bd.  iii),  devotes  much  space  to  these 
recurring  varieties,  describing  the  individual  phenomena  with  some 
minuteness  while  apparently  overlooking  in  general  the  most  essen- 
tial elements. 

These  intercurrent  forms  include  a  very  important  proportion 
of  all  strabismic  cases  in  the  early  stage.  Most  strabismic  children 
when  they  begin  to  squint  do  so  only  periodically.1  Xot  all  cases, 
however,  pass  to  the  state  of  permanent  squint,  a  certain  number  con- 
tinuing to  squint  periodically. 

The  periodical  forms  include: — 

1.  That  variety  in  which  no  decided  deviation  is  manifest  when 
the  eyes  are  in  perfect  repose,  but  immediately,  when  the  gaze  and 
the  attention  are  definitely  fixed  upon  a  given  object,  whether  at  near 
or  remote  distance,  a  squint  occurs. 

Many  persons  subject  to  this  form  of  strabismus  habitually  avoid, 
as  far  as  possible,  fixed  attention  with  the  eyes  upon  any  subject  for 
a  considerable  time.  In  conversation  they  glance  at  the  person  ad- 
dressed in  a  furtive  manner  and  at  once  turn  their  gaze  away.  They 
belong  to  the  class  of  which  it  is  said  "they  cannot  look  one  straight 
in  the  eye." 

If  these  cases  are  examined  by  the  phorometer,  tropometer,  and 
clinoscope,  they  are  found  to  have  greater  or  less  degrees  of  hyper- 
phoria,  generally  associated  with  anotropia,  or  r early  always  very 
marked  declinations,  generally  of  a  conjugate  character.  "When  the 
gaze  is  directed  listlessly  upon  the  ground  or  into  vague  distance  the 
visual  line  of  one  eve  often  rises  above  the  other.  There  is  either 


1  Von  Graefe,  following  Bohni,  regarded  the  periodic  form  as  the  ex- 
pression of  a  preliminary  period  of  the  "disease."  The  permanent  form  he 
regarded  as  the  secondary  stage  of  the  "disease." — Arch,  fiir  Ophthal.,  Bd. 
iii,  1,  p.  277  et  seq. 


394  ANOMALIES  OF  MOTOR  MUSCLES. 

vertical  diplopia  or  such  incomplete  union  of  the  images  of  the  two 
eyes  that  confusion  results  when  they  are  both  directed  toward  the 
point  of  attention.  The  slight  vertical  deviation  is  not  conspicuous, 
but  as  soon  as  the  attempt  is  made  to  direct  the  eyes  in  close  fixation, 
the  vertical  diplopia  or  the  confusion  from  the  imperfectly  united 
images  makes  it  necessary  that  the  axis  of  one  eye  should  turn  away 
from  the  direction  of  the  other  in  order  that,  by  a  more  considerable 
removal  of  the  double  images,  the  visual  confusion  may  be  relieved. 

2.  In  another  class   the   eyes   do  not  appear  to   abandon  their 
normal  relations  to  each  other  until  a  certain  point  of  proximity  is 
passed,  perhaps  at  one  or  two  feet,  or  more.     Within  the  limits  of 
this  distance  no  squint  is  observed,  but  beyond  it  strabismus  becomes 
manifest. 

Here,  too,  with  the  phorometer  and  the  tropometer  it  will  be 
found  that  the  images  do  not  lie  in  the  same  horizontal  plane,  but  that 
within  certain  limits  the  inequality  in  height  may  be  overcome.  Be- 
yond this  the  images  persist  in  remaining  vertically  separated,  and 
a  convergence  or  divergence  follows. 

3.  In   still    another   class   the    strabismus    occurs    only   at   near 
points.     Such  a  person  may  not  appear  to  squint  until  he  takes  a  book 
or  work  in  hand,  then  squinting  at  once  occurs. 

Like  the  two  forms  already  mentioned,  there  is  a  difference  in 
the  height  of  the  images,  in  this  case,  however,  becoming  uncon- 
trollable only  when  the  gaze  is  depressed  and  convergence  exercised. 
These  features  can  be  studied  and  located  when  we  are  careful  to 
examine  all  the  actions  of  the  eyes  in  their  relations  at  various  dis- 
tances and  in  various  planes  of  elevation  or  depression. 

There  is  no  exception  to  the  rule  in  these  cases  that  there  is  an 
unfavorable  adjustment  of  the  eyes  in  relation  to  the  horizontal  plane, 
affecting  the  direction  of  one  or  both  the  visual  lines.  There  is 
generally  hyperphoria  and  often  there  is  anotropia.  Declination 
here,  as  in  the  other  forms,  is  at  the  root  of  the  whole  matter,  induc- 
ing the  hyperphoria  which  in  turn  induces  the  convergence.  Von 
Graefe  believed  that  a  cure  for  these  cases  of  periodical  squint  could 
seldom  be  obtained.  And  very  natural  was  such  a  belief  when  he 
regarded  the  lateral  deviations  as  the  essential  defects. 

Taking  the  more  philosophical  view  resulting  from  investiga- 
tions which  we  are  now  able  to  make,  and  regarding  periodical  devia- 
tions as  the  expressions  of  unfavorable  adjustments,  there  is  no 
longer  any  occasion  for  this  gloomy  view  of  the  situation,  and  we 


CAUSES   OF   STRABISMUS.  395 

may  with  a  reasonable  degree  of  confidence  expect  not  only  to  be 
able  to  remove  the  unpleasant  appearance  of  squinting,  but  to  bring 
about  an  easy  and  normal  community  of  action  of  the  muscles  in  all 
positions  of  the  eyes. 

SECTION  LI. 
CAUSES  OF  STRABISMUS. 

Of  the  causes  assigned  for  the  deviations  of  concomitant  strabis- 
mus in  early  times,  many  appear  to  us  at  present  to  be  trivial.  The 
habit  of  placing  a  child  in  its  bed  often  in  the  same  position,  the 
imitation  of  a  nurse,  the  careless  neglect  to  use  one  eye  and  thereby 
permitting  it  to  squint,  these  and  many  other  such  supposed  influ- 
ences may  be  dismissed  without  discussion. 

A  small  number  of  cases  of  squint  occur  as  a  sequel  to  corneal 
scars,  lenticular  opacities,  and  other  obstructions  to  direct  vision  of 
one  eye.  Thus,  a  person  subject  to  central  blindness  of  one  eye,  as 
from  a  choroidal  atrophy,  occupying  the  vicinity  of  the  macula  lutea, 
may  cause  the  affected  eye  to  squint  in  order  to  bring  the  unaffected 
portion  of  the  fundus  in  line  with  the  object  and  the  pupil. 

These  various  incidental  causes,  however,  operate  in  only  a 
small  percentage  of  cases,  and,  indeed,  the  cases  cannot  in  general 
be  regarded  as  belonging  to  the  class  of  concomitant  strabismus.  In 
some  of  them,  as  in  certain  cases  of  corneal  or  lenticular  obstruction 
there  may  have  been  an  underlying  tendency  to  squint1  which,  so  long 
as  binocular  vision  remained  was  held  under  restraint. 

Passing  then  to  cases  of  clearly  defined  concomitant  strabismus, 
we  find  certain  phenomena  which  have  been  explained  on  many  hy- 
potheses, nearly  all  of  which  have  been  assumptions  not  based  upon 
natural  laws  or  upon  anatomical  research. 

There  is,  for  example,  the  hypothesis  that  the  inner  muscle  of 
the  squinting  eye  in  converging  strabismus  is  short  in  proportion  to 
the  other  muscles,  but  no  confirmation  of  this  hypothesis  has  been 
found  by  dissection  of  strabismic  eyes,  and  the  action  of  squinting 
eyes  when  the  patient  is  under  the  influence  of  anaesthetics  is  not 
consistent  with  the  theory.  Again,  the  external  muscle  of  the  same 
eye  in  the  same  form  of  squint  is  often  called  "the  weak  muscle," 


1  In  case  of  marked  declination  of  one  eye,  if  the  other  becomes  aphakic 
(operation  for  cataract,  etc.),  the  aphakic  eye  generally  swings  out  or  in, 
depending  on  the  direction  of  declination  of  the  sound  eye. 


396  ANOMALIES  OF  MOTOR  MUSCLES. 

yet  there  is  no  evidence  of  any  such  ''weakness."  Indeed,  it  is  very 
easy  to  show  that  neither  the  "short  muscle"  hypothesis  nor  the  as- 
sumption of  "weakness"  lias  any  part  in  the  jvtiology  of  concomitant 
strabismus  except  as  will  be  shown  as  we  proceed.1 

If  the  strabismic  eye  and  the  non-strabismic  eye  are  both  sub- 
jected to  the  test  of  the  tropometer,  the  power  of  the  muscles  and  the 
excursion  of  the  eye  will  be  as  great  in  the  case  of  the  squinting  as  in 
the  non-squinting  eye.  Such  exceptions  as  are  found  to  this  rule  can 
be  explained  upon  ordinary  mechanical  principles  and  do  not  con- 
stitute an  objection  to  the  statement.  For  example.,  the  cushion  of 
connective  and  fatty  tissue  forming  the  bed  in  which  the  eye  rests 
may  become  so  modified  by  the  habitual  rolling  of  the  eye  in  toward 
the  nasal  side  as  to  present  less  obstruction  than  exists  in  the  normal 
state  to  the  inward  rotation.  So  also  this  same  connective  tissue 
and  fat  cushion  may,  from  the  habitual  position  of  the  eye,  become 
a  mechanical  obstruction  to  the  free  rotation  inward. 

We  have  then  the  hypothesis  of  "cerebral  or  central  nervous 
troubles."  These  are  supposed  to  be  cerebral  troubles  developed  in 
infancy  and  causing  some  modification  in  the  function  of  conver- 
gence. When  we  inquire  as  to  the  nature  or  location  of  the  supposed 
cerebral  trouble  or  its  action,  when  we  attempt  any  practical  appli- 
cation of  the  hypothesis,  we  find  it  vague,  confused,  and  as  empty  of 
meaning  as  it  is  of  scientific  basis.  It  is  a  phrase  which  can  only 
serve  to  excuse  the  absence  of  definite  knowledge  which  it  is  supposed 
to  cover.  There  has  not,  in  any  case  of  concomitant  strabismus,  been 
observed  the  cerebral  condition  which  can  support  the  hypothesis  of 
a  cerebral  disease  as  a  cause  of  the  deviation.  The  fact  that  in  some 
instances  strabismus  and  infantile  convulsions  have  been  coincident 
does  not  sustain  the  doctrine,  nor  are  there  any  facts  that  do. 

We  come  now  to  an  assigned  cause  of  strabismus  which  has  been 
so  universally  accepted  that  it  is  necessary  here  either  to  conform  to 
the  almost  universal  belief  or  to  show  why  that  belief  is  not  well 
founded. 

1  Von  Graefe  says  tliat  squint  is  sometimes  the  expression  of  disease  of 
innervation.  sometimes  of  disease  of  the  muscle  structure,,  sometimes  of  ex- 
ternal causes  of  immobility,  and  sometimes  of  anomalies  of  vision.  In  these 
causes,  however,  he  includes  those  of  the  different  kinds  of  strabismus,  en 
comitant,  paralytic,  etc.  ("Beitrage  zur  Lehre  von  Schielen."  Arch,  fur 
Ophthalmologie,  iii,  1,  177.)  But  von  Graefe  did  not  regard  a  disease  of  inner- 
vation as. .the  cause  of  concomitant  squint.  He  says  (loo.  cit.,  p.  184)  that  ''the 
symptoms  of  concomitant  squint  are  independent  of  any  disease  of  innerva- 
ticm."  According  to  his  view  concomitant  strabismus  is  a  disproportion 
ptween  the  lengths  of  the  antagonizing  muscles. 


ACCOMMODATION  AND  CONVERGENCE.  397 


SECTION  LII. 

THE  RELATION  OF  THE  FUNCTION  OF  ACCOMMODATION  TO  THAT  OF 

CONVERGENCE.1 

The  views  of  no  man  have  been  more  universally  and  more  un- 
reservedly accepted  than  those  of  Bonders,  the  revered  investigator 
and  pioneer  in  modern  ophthalmology.  Personal  devotion  to  the  man 
has  been  added  to  professional  admiration  for  the  scholar.  Never- 
theless, as  new  facts  are  added  to  our  knowledge,  it  is  certain  that 
some  of  the  doctrines  taught  by  this  close  and  candid  observer  may 
be  fairly  investigated  anew  in  the  same  spirit  of  candor  which  he 
originally  brought  to  their  consideration. 

Bonders,  as  the  result  of  his  observations,  announced  two  im- 
portant propositions  in  regard  to  strabismus  which  he  formulated 
thus : — 

"1.  Strabismus  convergens  almost  always  depends 'upon  hyper- 
metropia. 

"2.  Strabismus  divergens  is  usually  the  result  of  myopia." 

The  argument  in  support  of  the  first  proposition  is  based  upon 
the  necessity  for  extraordinary  tension  of  the  accommodation  in 
hyperopia,  and  therefore  of  the  necessity  for  a  corresponding  exces- 
sive tension  of  convergence,  a  tension  which  at  length  results  in 
permanent  contracture  of  the  converging  muscles. 

Bonders  did  not  teach  that  this  connection  was  absolute  and 
necessary,  that  the  excess  of  tension  of  accommodation  in  hyper- 
metropia  must  inexorably  induce  an  excess  of  convergence,  as  had 
some  of  his  predecessors  in  the  same  field  of  inquiry.  He  recognized 
the  fact  that  under  certain  circumstances  the  relation  between  the 
two  functions  can  be  "at  least  partially  overcome." 

As  a  matter  of  fact,  is  there  any  such  physiological  connection 
between  these  two  functions  as  to  warrant  the  assertion  of  Bonders 
that,  "so  far  as  the  range  of  accommodation  for  both  eyes  extends, 
the  state  of  the  accommodation  of  the  eye  corresponds  to  a  definite 
convergence  of  the  visual  lines?" 

A  number  of  very  conspicuous  facts  are  in  conflict  both  with 
the  main  proposition  and  the  statement  just  quoted. 


1  The  substance  of  this  section  is  taken  from  a  paper  read  by  the  atithor 
at  the  International  Ophthalmological  Congress,  Edinburgh,  August  10.  1894. 


398  ANOMALIES  OF  MOTOR  MUSCLES. 

It  is  well  known  that  in  case  of  complete  paralysis  of  accom- 
modation occurring  suddenly  in  young  persons  the  function  of  con- 
vergence remains  undisturbed.  Cases  which  have  come  under  my 
observation  have,  when  examined  by  the  phorometer  both  during  the 
continuance  of  the  accommodative  paralysis  and  after  complete  recov- 
ery, shown  not  even  a  degree  of  excess  of  convergence  during  any 
stage  of  the  paralysis. 

Every  one  is  familiar  with  the  case  of  the  gradual  loss  of  accom- 
modation from  presbyopia  with  no  excess  of  convergence. 

The  converse  condition,  that  is,  the  loss  of  the  converging  power 
with  perfect  immunity  to  the  accommodation,  while  of  rare  occur- 
rence and  while  presenting  difficulties  in  the  examination,  does  not 
lead  to  the  conclusion  that  there  is  any  organic  relation  between  the 
two  functions.1 

Cases  long  since  reported  by  von  Graefe,  and  many  cases  re- 
ported by  others  since  then,  clearly  show  that  accommodation  is 
retained  in  paralysis  of  the  interni  and  in  ophthalmoplegia  externa. 

These  are  but  a  few  of  the  facts  from  the  point  of  view  of  the 
separate  performance  of  these  functions. 

Turning  to  the  anatomical  side  of  the  question  we  find  nothing 
to  sustain  the  propositions  of  Donders.  The  more  recent  investiga- 
tions of  the  anatomy  of  the  nerve  centers  controlling  these  functions 
show  not  only  that  the  nucleus  controlling  the  function  of  accom- 
modation is  distinctly  separated  from  that  governing  the  convergence, 
but  that  the  nerve  fibers  from  each  root  pass  separately  out  from  the 
brain,  and  that  they  are  only  united  within  a  common  sheath  after 
they  have  traversed  a  considerable  space  as  separated  fascicule. 

Such  considerations  suggest  that  these  two  functions,  which  usu- 
ally act  in  close  agreement,  so  act  as  a  result  of  habitual,  not  of 
organic  association. 

Training  or  a  necessity  which  interposes  important  obstacles  to 
the  habitual  association  of  action  quickly  enables  the  individual  to 
disassociate  the  two  functions  absolutely. 

Donders  supports  his  theoretical  view,  that  "strabismus  con- 
vergens  almost  always  depends  upon  hypermetropia,"  by  the  statis- 
tical results  of  his  investigations  concerning  the  refractive  condition 


1  Tn  a  valuable  paper  by  Prof.  C.  Hess,  of  Marburg,  at  the  International 
Congress  of  Ophthalmology,  Utrecht,  1899,  he  arrives  from  technical  considera- 
tions at  conclusions  similar  to  those  which  I  expressed  at  the  Edinburgh  Con- 
gress in  1894. 


ACCOMMODATION  AND  CONVERGENCE.  399 

of  strabismic  persons.  In  172  cases  of  strabismus  convergens  investi- 
gated by  him  hypermetropia  was  133  times  proved  to  exist  in  the 
undeviated  eye.1  Thus  hypermetropia  was  present  in  77  per  cent,  of 
his  cases.  In  many  of  these  cases  the  H.  was  completely  latent.2 
These  results  would  certainly  suggest  an  important  relation  between 
the  condition  of  squinting  and  the  condition  of  hypermetropia  if  we 
take  no  other  phase  of  the  investigation  into  consideration.  "When 
we  remember  that  in  the  extensive  examinations  of  pupils  in  schools 
which  have  been  reported  during  the  last  few  years  the  percentage 
of  hypermetropia  is  stated  by  the  examiners  to  be  from  66,  by  some 
examiners,  to  more  than  80  per  cent.,  by  others,  of  all  the  pupils,  it 
appears  at  once  that  the  percentage  of  hypermetropia  found  by  Bon- 
ders in  converging  strabismus  is  in  no  material  respect  different 
from  that  which  others  have  found  in  young  persons  in  general.  In 
other  words,  the  fact  that  Bonders  found  77  per  cent,  of  cases  of  con- 
verging strabismus  associated  with  hypermetropia,  manifest  or  latent, 
corresponds  with  the  fact  that  others  have  found  even  a  greater  pro- 
portion of  hypermetropic  cases  in  non-strabismic  people.3 

The  fact  of  greatest  interest  in  this  connection  and  that  which 
has  lent  more  support  to  the  theory  of  Bonders  than  all  other  facts, 
is  that,  by  the  use  of  convex  glasses,  converging  strabismus,  in  a  cer- 
tain proportion  of  cases,  disappears,  at  least  in  some  measure,  while 
the  glasses  are  in  front  of  the  eyes.  The  strabismus  in  these  cases 
returns  immediately  upon  removal  of  the  glasses. 

Such  a  striking  fact  cannot  be  ignored  nor  regarded  as  a  coin- 
cidence. The  deduction  is  natural  that  by  relieving  the  accommoda- 
tion, the  result  in  correcting  the  squint  must  be,  in  consequence  of 
such  relief,  to  the  accommodation. 

This  would  be  good  logic  if  the  convex  glasses  could  perform  no 
other  office  than  that  of  relieving  the  accommodation.  This  is  not 


x  "Accommodation  and  Refraction  of  the  Eye,"  p.  292. 

2  Loc.  cit.,  p.  193. 

3  In  Donders's  cases  and  in  the  cases  of  some  of  the  examiners  of  schools 
mydriatics  have  been  employed.      Practitioners  who  have  been  in  ophthalmic 
practice  for  several  years  must  have  observed  that  in  many  cases  in  which 
during  the  period  of  life  while  accommodation  was  active  atropine  has  revealed 
a  supposed  "latent  hypermetropia."  there  has  been  no  indication  of  hyperme- 
tropia when,  as  the  result  of  presbyopia,  years  later,  the  accommodation  has 
been    practically   abolished.      It    thus    appears   that   mydriatics   may   cause   a 
condition  of  apparent  hypermetropia,  which  is  not  the  normal  refractive  con- 
dition of  the  eye.     This  is  by  no  means  the  only  error  into  which  the  prac- 
titioner may  be  led  by  the  practice  of  paralysing  the  ciliary  muscle  with  the 
view  of  ascertaining  the  refractive  state  of  the  eyes. 


400 


ANOMALIES  OF  MOTOR  MUSCLES. 


the  fact.  Hence  the  deduction  does  not  follow  until  the  other  offices 
performed  by  the  glasses  are  examined  to  learn  whether  by  these  the 
same  result  may  be  reached.  Convex  glasses  may  act  as  prisms  and 
serve  to  relieve  a  hyperphoria. 

We  have  already  seen  that  hyperphoria  plays  an  important  role 
in  inducing  strabismus.  It  is  quite  possible  for  the  eyes  to  seek  such 
level  of  each  glass  as  to  find  such  a  prismatic  correction  of  hyper- 
phoria as  to  relieve  the  strabismus. 

The  example  shown  in  Figs.  158  and  159  will  illustrate  this 
proposition. 

The  young  girl  here  represented  had  used  3.50  D  spherical 
glasses  for  the  correction  of  her  strabismus.  The  eyes  looked  fairly 


Fig.  158.  Fig.  159. 

Showing  the  Correction  of  a  Converging  Strabismus  by  a  Weak 
Prism  with  its  Base  Down. 

straight  when  her  glasses  were  on,  but  the  right  turned  in  when  the 
glasses  were  off.  If,  however,  I  substituted  a  prism  of  4  diopters 
with  its  base  down  before  the  left  eye  (or  up  before  the  right)  exactly 
the  same  effect,  or  rather  a  better  one,  resulted. 

The  two  pictures  were  taken  at  the  same  sitting  within  one  min- 
ute of  each  other.  In  that  at  the  left  the  right  eye  squints  in.  Im- 
mediately on  placing  the  prism  before  the  left  eye  the  eyes  appear, 
as  in  the  figure  at  the  right,  parallel. 

It  is  an  advantage  of  the  spherical  glass  that  the  patient  may 
adjust  the  eyes  to  a  certain  degree  of  prism,  since  the  glass  is  a  prism 


CONVEX   GLASSES   AND   STRABISMUS.  401 

4 

of  increasing  strength  as  the  visual  line  passes  further  from  the  cen- 
ter. Concave  glasses  sometimes  serve  the  same  purpose  as  convex  in 
causing  a  temporary  relief  to  strabismus. 

The  strong  convex  glasses  may  serve  another  and  a  more  impor- 
tant office.  Acting  as  prisms,  but  not  in  the  direct  manner  of  a 
plane  prism,  the  image  seen  through  a  strong  spherical  glass  may  be 
subject  to  a  tilting  which  may  serve  to  neutralize  an  important  de- 
clination. 

Beyond  question  the  deviations  of  strabismus  are  in  close  rela- 
tion to  declinations.  If  then  the  eye  can  find  a  point  in  these  strong 
glasses  where  such  a  neutralization  can  be  found  the  strabismus  may 
disappear.  This  fact  is  excellently  illustrated  in  the  case  repre- 
sented by  the  three  following  figures: — 

The  young  woman  here  represented  had  had,  previously  to  my 


Fig.  160.  Fig.  161.  Fig.  162. 

Influence  of  a  Convex  Glass  in  Correcting  an  Inward  Deviation. 

knowledge  of  her  case,  three  very  free  tenotomies  for  converging 
strabismus. 

The  squinting  was  not  relieved  as  may  be  seen  by  the  first  figure. 
(Fig.  160.) 

Yet  the  medial  rotation  of  the  left  eye  was  nearly  destroyed. 
By  the  strongest  effort,  after  some  practice,  she  was  able  to  rotate 
that  eye  in  only  30°,  while  the  medial  rotation  of  the  other  eye  was 
60°. 

She  was  using  -j-  spherical  glasses  of  4.00  D.  With  these  the 
eyes  appeared  not  to  squint  in  but  out.  The  left  (.disabled)  eye  was 
invariably  in  fixation.  Tf,  while  she  looked  at  a  distant  object  a 
visiting  card  was  slipped  in  front  of  the  left  eye  the  right  eye  could 
be  seen  to  move  distinctly  toward  the  nose  and  occupy  the  position 


402  ANOMALIES  OF  MOTOR  MUSCLES. 

of  fixation,  while  the  other  wandered  out.  Thus,  although  the  con- 
vergence was  corrected,  a  divergence  of  nearly  equal  extent,  as  shown 
in  the  second  figure  (Fig.  161)  was  induced. 

Again,  if  a  -(-  5  D.  spherical  glass  was  placed  before  the  right  eye 
(which  was  generally  in  fixation  without  her  glasses)  the  left  at  once 
moved  out  and  up  with  a  very  distinctly  marked  twist  (Fig.  162), 
the  upper  end  of  the  vertical  meridian  moving  out.  If  placed  before 
the  left  eye,  the  action  was  less  emphatic  and  sometimes  failed. 

It  is  evident  that  in  this  case  the  neutralization  of  accommoda- 
tion is  not  the  means  through  which  the  strabismus  is  influenced. 
Each  eye  finds  a  point  in  the  lens  where  the  image  is  most  erect  and 
the  esotropia  is  changed  to  the  state  of  exotropia,  which  represents 
the  actual  adjustment,  since  one  of  the  interni  has  been  largely  dis- 
abled. 

Another  class  of  facts  may  be  shown  to  have  as  little  bearing 
upon  the  relation  of  accommodation  and  deviation.  The  cases  which, 
by  the  use  of  mydriatics  and  myotics,  are  temporarily  relieved,  are  not 
relieved  because  of  the  effect  upon  the  accommodation,  but  on  account 
of  the  effect  upon  vision. 

When  the  borders  of  objects  are  indistinctly  seen  there  is  less 
effort  to  correct  an  existing  declination,  and  hence,  generally,  less 
tendency  on  the  part  of  the  eyes  to  deviate  in. 

The  action  of  mydriatics  is  not,  however,  entirely  uniform  in 
this  respect.  I  have  observed  a  number  of  cases  in  which  converging 
strabismus  of  a  pronounced  character  has  been  induced  by  the  action 
of  mydriatics.  An  excellent  illustration  of  this  class  of  cases  may 
be  seen  at  pages  431  and  432,  where  Figs.  172  and  173  show  the  adjust- 
ments of  the  eyes  when  in  their  normal  state  and  when  under  the 
influence  of  atropine.  As  shown  at  Fig.  172  there  is  a  marked  exo- 
phoria  or,  perhaps  more  correctly,  a  slight  diverging  squint.  When 
the  eyes  of  the  patient  are  thoroughly  under  the  influence  of  atropine 
there  is  a  strongly  marked  converging  strabismus.  The  patient  whose 
eyes  are  thus  represented  had  in  childhood  marked  converging  squint 
which  she  "outgrew."  As  a  matter  of  fact  she  has  marked  declina- 
tions, and  when  she,  for  some  reason,  acquired  the  habit  of  fixing 
with  the  left  instead  of  the  right  eye,  the  strabismus  changed  from 
converging  to  diverging  on  the  basis  of  mechanical  laws. 

Thus,  of  all  the  facts  which  have  been  employed  to  sustain  the 
doctrine  of  the  dependence  of  squint  upon  hypermetropia,  not  one 
can  be  regarded  as  proof  of  the  doctrine. 


CAUSES  OF  STRABISMUS.  403 

Much  space  has  been  devoted  here  to  the  discussion  of  this  doc- 
trine, since  it  has  taken  so  firm  a  hold  upon  the  minds  of  ophthal- 
mologists who  have  accepted  it  on  the  authority  of  a  great  leader. 

It  would  be  even  less  difficult  to  show  that  the  doctrine  of  Don- 
ders's  second  proposition  is  not  founded  on  a  clear  conception  of  facts, 
but  what  has  been  said  respecting  the  first  proposition  must  serve  to 
show  that  there  is  not  sufficient  evidence  to  sustain  the  doctrine  of 
a  necessary  relation  between  accommodation  and  squint. 

Having  thus  discussed  in  the  negative  some  of  the  causes  which 
have  been  very  generally  accepted,  we  are  in  position  to  take  up  the 
subject  from  the  positive  side. 

Converging  strabismus  is,  in  not  a  few  instances,  largely  the 
result  of  the  instinctive  effort  to  force  the  visual  lines  into  the  same 
horizontal  plane  in  case  of  a  normal  tendency  of  one  of  these  lines 
to  rise  above  the  other.  This  condition  of  hyperphoria  or  perhaps 
of  hypertropia,  in  which  the  image  of  one  eye  tends  to  appear  above 
the  other  or  actually  rises  above,  is  a  state  of  the  vision  for  the  relief 
of  which  the  most  strenuous  efforts  will  be  made. 

That  this  is  in  many  cases  true  is  shown  by  the  fact  that  a 
tenotomy  properly  done  on  a  superior  rectus,  if  the  upward  rotation 
of  that  eye  is  excessive,  will,  in  an  important  proportion  of  strabis- 
mic  cases,  at  once  and  without  further  procedure  relieve  the  con- 
vergent squint. 

In  a  much  greater  number  of  cases  there  is  marked  anotropia. 
The  rotation  upward  of  a  very  large  percentage  of  cases  of  convergent 
squint  exceeds  45°  and  often  exceeds  50°  of  arc.  Here  the  extreme 
upward  tendency  of  the  eyes  imposes  upon  the  inferior  recti  an  ex- 
cessive tension  in  the  effort  to  bring  the  visual  lines  to  the  ordinary 
planes  of  direction,  and  this  tension  is  against  the  normal  tension 
of  the  superior  recti.  Owing  to  the  peculiar  insertion  of  the  superior 
and  inferior  recti  muscles  this  excessive  tension  constitutes  a  balance 
of  force,  in  a  majority  of  cases,  against  the  external  recti  which  is 
not  easy  to  resist. 

But  with  excessive  anophoria  there  are  generally,  or  at  least  very 
often,  extreme  declinations,  and  to  these  extreme  declinations,  de- 
clinations which  are  materially  emphasized  and  increased  by  the 
normal  torsions  in  looking  down  with  any  degree  of  convergence, 
more  than  to  any  other  one  cause  the  strabismic  deviations  are  due. 
If  the  eyes  were  not  set  too  high,  or  if  no  hyperphoria  existed,  the 
patient  might  control  the  declinations,  and,  conversely,  if  there  were 


404 


ANOMALIES  OF  MOTOR  MUSCLES. 


no  excessive  declinations,,  the  state  of  anophoria  would  not  induce  a 
squint.  Cases  already  mentioned  (Section  LI)  clearly  show  that 
the  squint  may  sometimes  be  relieved  by  reducing  the  plane  of  vision 
equally,  and  much  experience  shows  that  if  we  are  able  to  detect  and 
to  reduce  to  a  moderate  degree  the  extreme  declinations,  while  at 
the  same  time  the  anophoria  is  also  reduced,  the  squint  always  dis- 
appears. 

Strabismic  eyes  cease  to  be  strabismic  during  sleep,  but  with 
converging  squint  they  usually  roll  far  up,  directing  the  axis  toward 
the  brows.  Surgeons  who  have  frequently  operated  for  strabismus 
while  their  patients  have  been  under  the  influence  of  chloroform  are 


Fig.  163.  Fig.  164.  Fig.  165. 

Various  Forms  of  Deviation,  Depending  on  the  Choice  of  Fixation. 

familiar  with  the  fact  that  as  soon  as  the  anesthetic  influence  is 
established  the  squint  disappears.  It  has,  however,  escaped  general 
observation  that  the  eyes  roll  far  up,  under  the  upper  lids.  The 
observation  of  von  Graefe,  to  which  reference  has  already  been  made 
at  page  359,  that  with  convergent  strabismus  the  squinting  eye 
deviates  also  upward,  while  not  expressing  the  whole  truth  and  while 
not  correctly  interpreted  by  him,  is  of  much  importance  in  this  con- 
nection. 

In  Figs.  163,  164,  and  165  are  seen  illustrated  the  adjustments 
of  a  pair  of  strabismic  eyes,  the  directions  of  the  squint  depending 
on  whether  the  left  or  the  right  eye  is  in  fixation  or  whether  the  pa- 
tient attempts  to  fix  with  both  eyes.  In  each  instance  the  eyes  deviate 


CAUSES  OF  STRABISMUS.  405 

in  respect  to  the  demand  for  the  correction  of  the  peculiar  declina- 
tion. Thus,  in  the  first  figure  the  left  eye  is  in  fixation,  and  the 
right,  with  its  extreme  negative  declination,  turns  in.  In  the  next 
figure  the  right  eye  is  brought  into  difficult  fixation,  the  head  being 
turned  somewhat  to  aid  in  the  effort,  while  the  left  eye  (with  its 
positive  declination)  is  really  (though  not  in  the  picture  apparently) 
in  a  state  of  divergence  when  the  axes  of  vision  are  considered.  This 
can  be  shown  in  this  case  by  slipping  a  visiting  card  before  the  right 
eye,  when  at  once  the  left  eye  moves  in  toward  the  nose,  but  the  head 
turns  to  the  right. 

If  the  patient  looks  vaguely,  seeing  nothing  very  distinctly,  she 
is  able  to  direct  both  eyes  approximately  toward  the  same  object  (as 
in  Fig.  165). 

In  general,  if  the  squinting  eye  in  either  case  is  made  to  assume 
the  position  of  fixation,  the  other  eye,  when  it  takes  the  position 
known  as  "secondary  squint,"  also  squints  up.  Thus,  not  only  does 
the  deviating  eye  squint  up,  but  the  "sound"  eye,  when  it  becomes 
the  deviating  eye,  also  squints  up. 

This  phenomenon  can  in  most  cases  be  observed  if  a  visiting  card 
is  passed  alternately  before  one  and  the  other  eye. 

In  the  smaller  number  of  cases  in  which  the  adjustment  of  the 
axis  of  one  eye  is  nearly  coincident  with  the  plane  of  the  horizon 
while  the  other  eye  deviates  above  it,  in  other  words,  in  the  cases  in 
which  there  is  simply  hypertropia  with  the  converging  squint,  the 
vertical  deviations  of  the  two  eyes  will  be  in  opposite  directions,  as 
in  the  case  above,  when  each  is  in  turn  behind  the  little  screen.  In 
diverging  squint  the  deviating  eye  is  more  likely  to  deviate  down  as 
well  as  out. 

One  or  other  of  these  forms  of  vertical  deviation  exists  in  all, 
and  may  be  observed  in  this  simple  manner  in  nearly  all  cases  of  lat- 
eral squint,  whether  diverging  or  converging,  but  care  and  patience 
are  sometimes  required  for  the  observation,  and  in  exceptional  instances 
other  methods  must  be  resorted  to  if  we  would  demonstrate  the  char- 
acter of  the  vertical  deviation. 

In  Figs.  147,  148,  and  149  are  seen  illustrations  of  the  prin- 
ciple above  mentioned.  Figs.  147  and  148  are  from  photographs  of 
patients  with  concomitant  strabismus.  In  each  case  the  squinting  eye 
is  seen  to  deviate  not  only  inward,  but  strongly  upward.  In  Fig.  149 
is  represented  a  case  of  paralysis  of  the  externus  of  the  right  eye. 


4CG 


ANOMALIES  OF  MOTOR  MUSCLES. 


Here  it  is  easy  to  observe  that  the  deviation  is  not  in  an  oblique 
direction  as  in  the  other  cases,  but  directly  in. 

These  phenomena  in  concomitant  strabismus  are  not,  as  von 
Graefe  supposed  the  upward  turning  to  be,  simply  associated  phe- 
nomena, depending  in  some  undefined  manner  upon  the  inward 
deviation;  they  are  essential  elements  of  the  squint,  depending  upon 
the  direction  of  the  declination  and  the  hyperphoria,  which  is  usually 
itself  the  effect  of  the  declinations. 

It  is  not  difficult  to  find  the  reason  for  the  declinations.  Exam- 
inations of  carefully  made  dissections  suggest  at  once  the  probability 


Fig.  166. — Insertion  of  Tendons. 


that  the  meridians  of  eyes  cannot  be  uniformly  directed  in  all  cases. 
If  we  select  any  individual  muscle  and  examine  its  attachments  to 
the  sclera  in  different  cases  we  are  sure  to  find  variations. 

The  diagrams,  Fig.  166,  representing  the  upper  and  under  sur- 
faces of  two  eyes  and  indicating  the  insertions  of  the  superior  and 
inferior  recti  muscles  in  these  two  cases  serve  as  illustrations  of  the 
possible  variations  of  the  insertions  of  all  the  motor  muscles  in  dif- 
ferent eyes.  But  these  diagrams  were  not  made  to  show  this  fact; 
they  are  copied  from  the  interesting  monograph  by  Leopold  Weiss, 


HEREDITY  OF  STRABISMUS.  407 

"Uber  das  Wachstum  des  Menschlichen  Auges,"1  etc.,  and  which  are 
here  inserted  by  his  kind  permission. 

If  we  compare  the  insertions  of  corresponding  muscles  in  these 
two  eyes,  and  if  the  remaining  insertions  are  no  more  uniform  than 
the  two  pairs  shown,  it  must  be  assumed  that  both  pairs  of  eyes  can- 
not be  adjusted  with  the  same  relation  of  the  vertical  meridian  to  an 
actual  vertical  position.  But  it  is  extremely  probable  also  that  the 
development  of  the  bony  walls  of  the  orbits  are  even  more  instru- 
mental in  the  aetiology  of  declinations.2 

Undoubtedly  the  form  of  the  orbit  has  a  great  and,  in  many 
cases,  a  prevailing  influence,  as  has  been  suggested  in  Section  XXIV. 

Katophoria  is  much  less  frequently  the  cause  of  strabismus  con- 
vergens  among  Anglo-Saxons  than  anophoria. 

On  the  contrary,  katophoria  is  frequently  associated  with  di- 
verging strabismus. 

Diverging,  like  converging  strabismus,  may  have  its  origin  in 
anotropia,  when  the  combination  of  declinations  is  favorable  to 
induce  divergence. 

SECTION  LIU. 

HEREDITY  OF  STRABISMUS. 

Strabismus  often  prevails  in  families.  It  is  not  uncommon  to 
see  several  members  of  a  family  with  about  the  same  form  of  squint. 

Among  the  reports  of  numerous  instances  of  squint  in  the  same 
family  may  be  mentioned  that  of  Stratfield,3  who  examined  seven 
cases  of  converging  squint  in  the  same  family,  yet  the  parents  of 
these  children  did  not  squint.  I  have  reported  a  family4  in  which 
were  five  children,  all  of  whom  squinted.  In  another  family  which 
I  have  seen,  more  recently,  all  the  five  children  had  converging 
strabismus,  and  I  am  informed  that  the  father  had  strabismus  as  a 
child,  but  had  an  operation  for  it. 

It  should  be  added  that  neither  of  these  children  had  any  very 
marked  refractive  error  and  some  of  them  had  none. 

From  what  has  been  said  of  the  inherited  form  of  the  orbits, 
with  resulting  anophoria  and  declinations,  the  line  of  this  hereditary 
defect  is  clearly  indicated. 

l"Referate  und  Entwickelungs  Geschichte."  Weisbaden. 

2  See  page  299. 

3  Ophthalmic  Hospital  Reports,  vol.  i,  1859. 
*  ''Functional  Nervous  Diseases,"  p.  154. 


408  ANOMALIES  OF  MOTOR  MUSCLES. 

SECTIOX  LIV. 
A  TABLE  OF  STRABISMUS  CASES. 

In  a  number  of  works  on  the  subject  of  strabismus  statements  appear  in 
regard  to  the  proportion  of  certain  forms  of  refractive  anomalies  to  each  of 
the  generally  recognized  forms  of  strabismus,  the  converging  and  the  diverging. 

In  these  statements,  however,  there  appear  no  details  or  very  imperfect 
details  of  the  various  conditions,  and  from  these  indefinite  data  important  and 
erroneous  conclusions  have  been  drawn. 

It  has  been  thought  advisable,  even  at  the  expense  of  considerable  space, 
to  place  before  the  reader  a  series  of  consecutive  cases  sufficiently  extensive 
to  furnish  grounds  for  reasonable  deductions,  in  which  a  more  detailed  state- 
ment than  has  heretofore  appeared  may  permit  of  a  closer  analysis  of  the 
various  conditions  which  may  be  found  coexisting  with  strabismus.  The 
table  consists  of  immediately  consecutive  cases  in  the  order  in  which  they 
appear  on  the  case-books,  with  a  few  exceptions  in  cases  of  infants  in  which 
the  examinations  have,  of  necessity,  been  too  imperfect  to  be  of  value  in  this 
connection.  In  the  great  majority  the  record  is  the  outcome  of  a  number  of 
examinations  resulting  generally  in  the  ability  of  the  patients  to  locate  the 
double  images  and  therefore  to  permit  of  more  or  less  accurate  measurements 
of  the  various  deviations.  In  a  few  cases  other  methods  have  been  resorted 
to.  While  in  this  small  group  the  results  are  necessarily  less  perfect  than  in 
the  other,  they  do  not  vary  so  essentially  from  true  results  as  to  detract  ma- 
terially from  the  value  of  the  table. 

No  cases  of  paralysis  or  of  deviations  from  other  pathological  conditions 
have  been  admitted  to  the  list. 

As  the  table  was  at  first  prepared  it  contained  400  cases,  but  on  exami- 
nation it  was  found  that  the  summary  of  results  did  not  vary  materially 
whether  the  whole  number  or  only  the  number  retained  was  used. 

An  important  omission  of  this  table  is  found  in  the  absence  of  statement 
in  each  case  of  the  vertical  and  horizontal  rotations  as  they  may  be  determined 
by  the  tropometer.  This  omission  arises  from  the  fact  that  the  table  includes 
some  cases  which  were  examined  either  before  the  tropometer  was  introduced 
or  before  it  was  brought  to  its  present  state  of  perfection.  A  statement  of 
results  of  examination  by  the  tropometer  in  strabismic  cases  will  be  found 
elsewhere. 

It  is  to  be  remembered  that  this  table  does  not  deal  with  cases  of  simple 
heterophoria,  cases  in  which  single  vision  may  exist  notwithstanding  some 
hindrances.  Every  case  is  one  in  which  single  vision  was  unattainable  by  the 
patient.  In  looking  over  the  cases  the  numbers  representing  the  degrees  of 
deviation  may  appear  small.  In  such  cases  by  means  of  prisms  which  have 
served  to  bring  the  images  into  proximity  the  impulse  toward  binocular  vision 
has  been  sufficient  to  unite  images  at  the  expense  of  effort  on  the  part  of  the 
directing  muscles  of  the  eyes.  With  a  deviation  in  the  vertical  direction  rep- 
resented by  a  very  small  number  of  degrees,  it  is  in  many  cases  impossible  to 
maintain  or  even  temporarily  to  achieve  single  binocular  vision. 


TABLE  OF  ELEMENTS  IN  STRABISMUS. 


409 


Table  Giving  in  Degrees  the  Elements,  Exotropia,  Esotropia,  and  Hypcrtropia, 
icith  the  Refraction  in  Two  Hundred  Immediately  Consecutive  Cases  of 
Strabismus  Seen  in  Private  Practice. 


No. 

Esotropia. 

Exotropia. 

Hypertropia. 

Myopia. 

Hyperopia. 

Emme- 
tropia. 

1 

10° 

// 

2 

12° 

// 

3 

20° 

// 

4 

20° 

2° 

4.50 

5 

7° 

15.00 

6 

20° 

14° 

6.00 

7 

8° 

3° 

// 

8 

13° 

2° 

// 

9 

14° 

4° 

4.50 

10 

18° 

6° 

22.00 

11 

45° 

10° 

// 

12 

9° 

// 

13 

15° 

5.50 

14 

30° 

8° 

// 

15* 

10° 

7° 

// 

16 

16° 

// 

17 

28° 

7° 

50 

18 

15° 

// 

19 

11° 

3° 

// 

20* 

15° 

20° 

4.00 

21 

10° 

// 

22 

12° 

3.50 

23* 

37° 

3° 

// 

24 

17° 

// 

25 

45° 

7° 

1.75 

26 

18° 

6.00 

27 

35° 

8° 

6.00 

28 

7° 

// 

29* 

17° 

19° 

// 

30 

35° 

12° 

1.00 

31 

10° 

1.00 

32 

40° 

10° 

4.00 

33 

20° 

// 

34 

40° 

10° 

// 

35 

18° 

6° 

22.00 

36 

35° 

7° 

// 

37 

40° 

15° 

// 

38* 

9° 

// 

39 

18° 

1° 

.50 

40 

8° 

1.00 

41 

16° 

1.50 

42 

28° 

7° 

1.00 

43 

35° 

5° 

19.00 

44 

14° 

.50 

45 

6° 

3° 

// 

46 

5° 

4° 

11.00 

47 

8° 

2° 

.50 

48 

9° 

2° 

.75 

49 

6° 

// 

50 

18° 

5.00 

51 

11° 

2° 

2.00 

Cases  marked  by  an  asterisk  (*)  had  been  operated  on  for  strabismus  before  consulting  me. 


410 


ANOMALIES  OF  MOTOR  MUSCLES. 


No. 

Esotropia. 

Exotropia. 

Hypertropia. 

Myopia. 

Hyperopia. 

Enime- 
tropia. 

52 

8° 

2.75 

53 

20° 

4° 

6.00 

54 

20° 

4° 

.20 

55 

8° 

2° 

2.00 

56 

12° 

2° 

275 

57 

14° 

4° 

10.00 

58 

10° 

2° 

.50 

59 

16° 

8° 

3.00 

60 

20° 

4° 

2.00 

61 

27° 

15° 

// 

62 

9° 

20° 

1.50 

63 

10° 

1.50 

64 

7° 

2° 

5.00 

65 

15° 

2° 

.50 

66 

6° 

20° 

1.50 

// 

67 

11° 

68 

7° 

2° 

4.50 

69 

7° 

2° 

.50 

70 

16° 

2° 

71 

15° 

8° 

4.00 

// 

72 

7° 

10° 

1.75 

73 

1° 

8.00 

74* 

20° 

// 

75 

14° 

3° 

.50 

76 

50° 

3.00 

77 

30° 

18.00 

78 

20° 

6° 

// 

79 

8° 

10° 

8.00 

80 

20° 

1  25 

81 

6° 

12° 

// 

82 

12° 

4° 

// 

83 

30° 

8° 

// 

84 

20° 

ft 

85 

30° 

8° 

// 

86 

12° 

2° 

ft 

87* 

2° 

7° 

.50 

88 

15° 

.75 

89 

16° 

1.50 

90 

15° 

.75 

91* 

15° 

1.00 

92 

7° 

7° 

// 

93 

16° 

3° 

.75 

94 

19° 

10° 

5.00 

95* 

40° 

12° 

// 

96 

20° 

7° 

4.00 

97 

20° 

3° 

4.00 

98* 

15° 

ff 

99 

10° 

.50 

100 

7° 

800 

101 

5° 

6° 

5.00 

102 

16° 

5° 

2.00 

103 

16° 

// 

104 

40° 

2.50 

105 

40° 

8° 

// 

106 

12° 

.50 

107 

50° 

10° 

3.00 

108* 

13° 

8° 

1.50 

Cases  marked  by  an  asterisk  (*)  had  been  operated  on  for  strabismus  before  consulting  me. 


TABLE  OF  ELEMENTS  IN  STRABISMUS. 


411 


No. 

Esotropia. 

Exotropia. 

Hypertropia. 

Myopia. 

Hyperopia. 

Emme- 
tropia. 

109 

26° 

6° 

110 

15° 

// 

111* 

30° 

10° 

1.00 

// 

113 

5° 

4° 

113 

45° 

10° 

// 

114 

10° 

2.00 

115 

6° 

2° 

.75 

116 

8° 

2.75 

117* 

10° 

ft 

118 

32° 

10° 

// 

119* 

4° 

// 

120 

30° 

4° 

1.00 

121 

8° 

// 

122 

6° 

// 

123 

25° 

13° 

.50 

124 

20° 

// 

125 

30° 

3.50 

126 

28° 

4° 

// 

127* 

13° 

3° 

1.00 

128 

20° 

175 

129 

10° 

4° 

1.00 

130 

40° 

// 

131 

8° 

3° 

14.00 

132 

50° 

// 

133 

20° 

6° 

// 

134 

20° 

10° 

// 

135 

14° 

2.50 

136* 

8° 

2.00 

137 

20° 

12° 

// 

138 

12° 

3.00 

139* 

15° 

3° 

// 

140 

5° 

5.00 

141 

13° 

5° 

1.00 

142* 

15° 

2.00 

143 

35° 

// 

144* 

18° 

12° 

.50 

145 

17° 

3.00 

146* 

12° 

3° 

// 

147 

14° 

2° 

.50 

148 

15° 

12° 

// 

149 

20° 

6° 

200 

150 

12° 

.50 

151 

16° 

1.00 

152 

10° 

2° 

// 

153 

35° 

12° 

1.00 

154 

7° 

5° 

// 

155 

25° 

12° 

// 

156 

17° 

25.00 

157 

35° 

3.00 

158 

15° 

3.00 

159 

11° 

2.50 

160 

20° 

12° 

// 

161 

4° 

5° 

5.00 

162 

24° 

13.00 

163 

6° 

4° 

2.50 

164 

35° 

6.00 

165 

12° 

9° 

.50 

Cases  marked  by  an  asterisk  (*)  had  been  operated  on  for  strabismus  before  consulting  me. 


412 


ANOMALIES  OF  MOTOR  MUSCLES. 


No. 

Esotropia. 

Exotropia. 

Hypertropia. 

Myopia. 

Hyperopia. 

Emme- 
tropia. 

166 

16° 

4.50 

167 

15° 

.50 

168 

15° 

5° 

.50 

169 

6° 

3.00 

170 

35° 

8° 

// 

171 

30° 

18° 

6.00 

]72 

40° 

7° 

1.75 

173 

17° 

//  • 

174 

37° 

3° 

// 

175 

12° 

2°         2.00 

176 

16° 

1° 

.50 

177 

15° 

2° 

1.00 

9.00 

178 

15° 

2.50 

179 

50° 

1° 

4.50 

180 

11° 

4° 

.50 

181 

30° 

// 

182 

15° 

4° 

// 

183 

10° 

// 

184 

20° 

// 

185 

20° 

5° 

// 

186 

12° 

1.25 

187 

25° 

4° 

1.25 

188* 

20° 

4° 

4.50 

189 

12° 

1.00 

190 

35° 

10° 

11.00 

191 

15° 

// 

192 

16° 

.50 

193 

12° 

1.00 

194 

12° 

6° 

3.50 

195* 

16° 

1.00 

196* 

20° 

// 

197 

45° 

5° 

1.00 

198 

25* 

4.00 

199 

19° 

10° 

// 

200 

15° 

.75 

NOTE.— 126  has  diverging  strabismus,   or  converging,  since  operation,   some  years  since. 
Cases  marked  by  an  asterisk  (*)  had  been  operated  on  lor  strabismus  before  consulting  me. 

Of  this  whole  number,  200,  there  are  86  in  which,  by  the  num- 
bers representing  degrees,  the  condition  of  exotropia  or  outward 
turning  is  the  predominating  element  of  the  deviation. 

There  are  68  cases  in  which,  by  the  same  indication,  the  condi- 
tion of  esotropia  or  inward  turning  is  the  principal  element  of  the 
deviation. 

In  46  cases  hypertropia  or  strabismus  sursumvergens  constitutes 
the  principal  deviating  element. 

It  is  thus  seen  that  of  these  consecutive  cases  42  per  cent,  are 
cases  of  exotropia,  331/2  per  cent,  esotropia,  and  24!/o  per  cent,  are 
hypertropia. 

Judging  simply  by  the  figures  indicating  the  degrees  of  the  dif- 


TABLE  OF  ELEMENTS  IN  STRABISMUS.  413 

ferent  elements  of  the  deviations,  it  would  appear  that  the  condition 
of  hypertropia  occurs  with  less  frequency  than  either  esotropia  or 
exotropia.  This  would  be  entirely  a  superficial  view,  for  a  large  per- 
centage of  those  which,  by  this  method  of  calculation,  are  placed  in 
the  lists  of  lateral  deviations,  is  in  fact  made  up  of  cases  in  which 
the  element  of  hypertropia  is  most  important,  and,  indeed,  one 
accustomed  to  observe  the  relations  between  these  conditions  will 
recognize  in  the  hypertropic  condition  one  of  the  essential,  if  not 
the  most  essential,  of  the  deviating  elements. 

For  example,  Xo.  6,  with  a  vertical  deviation  of  14°,  is  classed 
with  exotropia  because  there  is  a  lateral  deviation  of  20°,  but  who 
can  doubt  that  the  latter  is  a  swing  caused  by  the  former?  In  such  a 
case,  if  the  vertical  deviation  were  to  be  fully  and  exactly  corrected 
while  at  the  same  time  the  vertical  meridians  were  to  be  made  to 
assume  a  true  vertical  position,  exotropia  would  at  once  disappear  and 
single  vision  would  be  completely  established  (as  was  actually  the 
case  in  this  instance).  Taking  this  view  we  should  include  in  the 
list  of  hypertropic  cases  Xos.  6,  10,  11,  14,  17,  27,  30,  and  many 
others.  I  have,  in  the  summary  of  exotropic  and  esotropic  cases  above 
stated,  included  in  the  numbers  cases  of  hypertropia  which,  were  they 
removed  to  the  list  of  hypertropic  cases,  would  bring  the  list  to  not 
less  than  101  cases,  or  more  than  one-half  in  which  hypertropia  is 
the  essential  element  of  the  deviation. 

Experience  has  shown  that  in  the  great  majority  of  these  actual 
cases  a  correction  of  the  hypertropia  has  been  the  only  treatment  re- 
quired to  relieve  the  lateral  deviation,  not  only  to  appearances,  but 
largely  as  shown  by  careful  phorometric  tests. 

The  fact  of  the  existence  of  hypertropia  in  so  many  of  these 
cases  which  had  already  been  operated  on  by  tenotomy  of  the  interni 
before  coming  into  this  list  is  of  great  importance. 

The  table  also  shows  the  refraction  of  these  cases,  from  which  it 
appears  that  of  the  cases  of  exotropia,  23  are  myopic,  38  hyper- 
metropic,  and  23  emmetropic.  In  cases  of  ametropia  the  eye  having 
the  greatest  defect  has  been  chosen  as  that  representing  the  refrac- 
tion. 

Of  the  esotropia  cases,  18  are  myopic,  20  are  hyperopic,  and  29 
are  emmetropic. 

Among  the  cases  of  hypertropia,  14  are  myopic,  13  are  hyperopic, 
and  21  are  emmetropic. 

These  cases,  therefore,  do  not  sustain  the  view  that  converging 


414  ANOMALIES  OF  MOTOR  MUSCLES. 

strabismus  is  caused  principally  by  hypermetropia,  nor  that  diverging 
strabismus  is  almost  always  caused  by  myopia.  Among  the  cases  of 
converging  deviation,  hypermetropia  and  myopia  are  almost  equally 
frequent,  Avhile  of  the  cases  of  diverging  strabismus,  23  only  are 
myopic,  while  38  are  hypermetropic,  and  23  emmetropic.  The  hy- 
permetropic  cases  that  accord  with  converging  squint  are  in  a  less 
percentage  than  has  been  found  among  the  pupils  of  schools  by  some 
examiners. 


SKCTIOX  LV. 

TREATMENT  OF  STRABISMUS. 

In  the  introduction  devoted  to  the  history  of  the  knowledge  of 
strabismus  it  has  been  shown  how,  after  the  trial  of  many  unsuccessful 
devices,  the  treatment  by  tenotomy  was  introduced,  first,  perhaps  by 
Taylor,  of  whose  methods  we  know  very  little,  and  then  by  Stroh- 
meyer  and  Dieffenbach,  who  gave  to  the  world  the  benefit  of  their 
researches  and  experiences. 

From  this  point  the  investigation  of  the  phenomena  and  nature 
of  the  defect  proceeded  rapidly,  with  the  introduction  of  many  ad- 
vances and  some  retrograde  movements  in  the  treatment. 

The  earlier  operations  of  Dieffenbach  consisted  of  a  section  of 
the  tendon  of  the  rectus  muscle,  internal  or  external,  not  far  from  the 
sclera.  The  details  of  the  procedures  were  complicated  and  imper- 
fect, yet  in  many  moderate  cases  a  marked  improvement  in  the  ap- 
pearance of  the  patient  was  gained.  Cunier,  Lucien  Boyer,  Listen, 
Bonnet,  and,  in  America,  Dix,  were  among  the  many  who  adopted 
and  in  some  respects  simplified  the  operations.  The  "cure"  of  strabis- 
mus quickly  became  a  show  operation,  and  was  performed  before 
wondering  crowds.  As  might  have  been  expected,  the  results  became 
less  and  less  favorable.  In  order  to  "cure"  the  more  extravagant 
cases  the  muscle  was  cut  farther  and  farther  back  until  a  "myotomy" 
was  equivalent  to  a  paralysis.  Even  worse,  for  the  straightened  eye, 
if  it  did  not  turn  in  the  opposite  direction  during  the  operation,  lost 
little  time  in  so  doing  after  it,  and  the  last  state  of  the  patient  was 
infinitely  worse  than  the  first. 

The  zeal  in  completely  severing,  not  only  the  muscle  itself,  but 
all  its  connective  tissue  surroundings,  so  increased  that  it  was  not 
unusual  to  completely  myotomize  all  the  four  recti  in  a  single  case. 


TREATMENT   OF  STRABISMUS.  415 

Thus,  Baudens1  says  that  about  once  in  twenty  or  thirty  cases  it  is 
necessary  to  cut  the  internal,  superior,  and  inferior  recti,  and  he  also 
adds  that  not  unfrequently  is  it  necessary  to  divide  not  only  all  the 
four  recti  muscles,  but  that  the  superior  or  inferior  oblique  should 
be  divided  as  well. 

To  such  extremities  had  these  myotomies  reached  that  at  length 
many  of  the  more  reputable  surgeons  declined  to  operate  for  strabis- 
mus. Considerable  reaction  had  already  taken  place  when  von  Graefe 
gave  the  influence  of  his  great  authority  to  a  more  moderate  and 
reasonable  treatment.  It  was  fortunate  that  so  many  had  abandoned 
the  operation,  for  there  was  no  practical  opposition  to  the  method 
advised  by  von  Graefe  and  a  return  to  the  original  principles  of  the 
operation  with  the  improved  methods  completely  succeeded  to  the 
wild  rage  for  myotomies. 

Coincident  with  the  return  to  more  moderate  surgical  treatment, 
prophylactic  and  Avhat  were  regarded  as  curative  measures  without 
operations  were  introduced,  based  upon  the  refractive  or  accommoda- 
tive state  of  the  eyes.  Cases  of  intercurrent  strabismus  were  care- 
fully watched  in  the  beginning  in  the  hope  of  avoiding  the  almost  in- 
evitable permanent  squint.  Some  of  these  methods  are  still  extant, 
and  are,  at  least  under  certain  circumstances,  useful.  To  some  of 
these  we  will  first  direct  attention. 

Of  these  prophylactic  measures,  the  most  important,  in  the  very 
early  years  of  childhood,  is  restraint  from  the  use  of  the  eyes  for 
close  attention  to  any  occupation  demanding  accurate  visual  adjust- 
ments at  near  points.  It  is  certainly  better,  taking  whatever  view  we 
may  of  the  aetiology  of  strabismus,  that  the  strabismic  habit  should 
not  be  established.  Also,  taking  any  of  the  more  modern  views,  a 
strabismic  condition  being  once  established,  it  is  difficult  to  restore 
the  eyes  to  a  state  of  perfect  coordination. 

Hence,  if  intercurrent  strabismus,  even  of  a  slight  degree  or  of 
somewrhat  rare  occurrence,  is  observed,  the  child  should  be  discour- 
aged from  close  occupations  demanding  the  use  of  the  eyes  until  it  is 
of  such  an  age  that  suitable  examinations  and  more  definite  prophy- 
lactic measures  can  be  brought  to  bear. 

Attendance  at  school  or  kindergarten,  the  learning  to  read  and 
write  and  games  in  which  the  eyes  are  brought  into  close  use  should 
be  deferred,  and  when  it  is  not  practicable  absolutely  to  prevent  such 


1  Gazette  des  Hopitaux,  1841. 


416  ANOMALIES  OF  MOTOR  MUSCLES. 

uses  of  the  eyes,  the  hours  of  study  or  of  play  with  near  objects  should 
be  limited  to  the  minimum. 

Children  subject  to  periodic  strabismus  are  often,  if  not  usually, 
wanting  in  physical  force;  they  are  known  as  "delicate"  children, 
often  extremely  nervous  and  active,  but  rarely  strong  to  resist  un- 
favorable physical  influences. 

Such  children  should  be  sustained  by  a  systematic  regimen  in 
regard  to  food,  which  should  be  nourishing  and  easy  of  digestion,  and 
the  use  of  tonic  medicines  may  be  required  in  addition  to  other  hy- 
gienic measures.  By  such  precautions  the  fixed  strabismic  habit  may 
often  be  somewhat  delayed,  and  thus  time  may  be  gained  for  more 
radical  measures. 

The  views  of  Bonders,  that  the  hypermetropic  state  of  the  eyes 
is  usually  the  cause  of  converging  strabismus  naturally  led  to  the  use 
of  convex  glasses,  not  only  as  a  prophylactic  means,  but  as  a  cure. 
We  have  already  seen  that  the  doctrine  is  not  based  on  sufficient  data ; 
yet,  without  accepting  the  dogma  of  the  relation  between  hyper- 
metropia  and  converging  strabismus,  we  may  still  regard  the  adjust- 
ment of  suitable  glasses  for  the  correction  of  important  refractive 
anomalies  as  among  the  most  important  and  essential  of  preventive 
measures. 

By  means  of  the  ophthalmoscope,  especially  by  skiascopic  exami- 
nations, at  least  conspicuous  refractive  anomalies  may  be  correctly 
diagnosed  in  very  young  children. 

The  correction  of  such  important  anomalies  by  suitable  glasses 
may  serve  several  purposes.  The  child  may,  by  the  relief  afforded  by 
the  glasses,  be  rendered  less  nervous  and  more  vigorous.  This  is 
important,  as  it  enables  the  patient  to  apply  a  greater  amount  of  sur- 
plus energy  to  the  muscles  of  the  eyes.  But  glasses,  whether  convex 
or  concave,  act  as  prisms  which  may  correct  hypcrphoria  and  also 
neutralize  declinations,  and  it  is  quite  possible  that  the  prismatic 
influence  of  a  pair  of  glasses  may  be  sufficient  to  delay  the  permanent 
deviation  of  the  eyes  until  a  more  important  correction  of  the  mus- 
cular anomaly  may  be  instituted.  Eeferring  to  page  400,  the  effect 
of  a  weak  prism  wrth  its  base  down  is  seen  to  be  of  the  most  striking 
character.  The  use  of  such  a  prism  after  the  strabismic  habit  has 
been  once  permanently  established  affords  only  temporary  relief  to 
the  lateral  deviation,  the  eyes  returning  to  their  incongruous  relations 
as  soon  as  the  prism  is  removed.  But  if  the  prism  could  be  used  at  a 
sufficiently  early  period,  the  occurrence  of  the  permanent  form  of 


TREATMENT   OF  STRABISMUS.  417 

deviation  might  often  be  avoided.  It  is  evidently  impossible  to  de- 
termine the  character  of  the  prism  to  be  used  in  the  cases  of  very 
young  children,  but  if  a  convex  spherical  glass  of  considerable 
strength  is  required  to  correct  a  hypermetropia,  the  eyes  themselves 
will  soon,  in  a  certain  proportion  of  cases,  make  such  a  selection  of 
the  positions  through  which  the  lines  of  regard  are  to  pass  that 
effective  prisms  are  found,  not  only  for  the  correction  or  partial  cor- 
rection of  hyperphoria,  but  for  the  correction  of  the  position  of  the 
image  of  a  vertical  line  upon  the  retina ;  and  the  effects  of  such  cor- 
rections will  go  far  to  arrest  the  squinting  habit. 

Of  late  simple  stereoscopic  figures  have  been  much  in  use  to 
prevent  the  permanent  deviation  of  the  eyes  of  those  showing  signs 
of  squint.  A  number  of  instruments  on  the  principle  of  the  stereo- 
scope are  made,  and  some  practitioners  believe  that  they  have  per- 
manently prevented  the  threatened  defect.  However  this  may  be, 
there  can  be  no  objection  to  such  a  method,  and  it  may  serve  at  least 
to  prevent  amblyopia. 

Children  who  have  reached  the  age  of  5  or  6  years  are  often 
remarkably  quick  and  exact  in  their  replies  to  the  tests  for  hetero- 
tropia,  hence  it  is  not  difficult  to  introduce  rational  treatment  at  an 
early  age.  Intelligent  and  tractable  children  are,  of  course,  able  to 
receive  earlier  and  better  attention  than  those  who  are  less  under 
control. 

We  have  already  seen  that,  in  general,  strabismus  is  the  sur- 
render to  the  difficulties  of  adjustments  of  the  vertical  meridians  or 
of  the  plane  of  vision. 

The  conditions  are  in  close  relation  to  the  form  and  direction 
of  the  orbit,  and  this  is  itself  in  relation  to  the  type  of  the  cranium. 

To  suppose  that  by  any  stimulus  to  the  nerves  governing  the 
movements  of  the  eyes  a  permanent  relief  to  this  condition  could  be 
expected,  would  be  to  assume  that  the  anatomical  relations  of  the 
intra-orbital  parts  could  be  changed  by  such  a  process. 

Xo  treatment  by  which  the  development  of  permanent  squint 
can  be  delayed  can  relieve  the  conditions  on  which  it  depends. 

By  one  means  and  by  one  only  can  the  unfavorable  directions 
of  the  visual  axes  or  of  the  vertical  meridians  which  lead  to  squint 
be  effectually  prevented  from  inducing  one  or  another  form  of  injury, 
and  that  is  by  radically  changing  the  anatomical  relations  of  the 
muscles  which  give  direction  to  the  axes  of  the  eyes  or  to  the  position 
of  the  meridians.  But  such  radical  change  cannot  be  effectually  ob- 

27 


418  ANOMALIES  OF  MOTOR  MUSCLES. 

tained  by  the  long-established  methods  of  severing  the  connections 
between  the  eyeball  and  the  tendon  of  the  muscle  toward  which  the 
eye  appears  to  swing,  leaving  the  tendon  to  fall  back  in  its  sheath. 
It  is  only  by  the  strict  observance  of  the  principles  which  have  been 
set  forth  in  this  volume,  principles  based  upon  the  mechanical  ten- 
sions, not  of  one,  but  of  all  the  muscles,  not  of  one,  but  of  both  eyes, 
that  the  strabismic  tendency  can  be  expected  to  yield.  It  is  the 
failure  to  look  at  strabismus  from  this  broad  view  that  has  made  it 
an  operation  for  a  comparative,  and  only  comparative,  cosmetic  relief 
to  an  unpleasant  deformity. 

The  object  aimed  at,  complete  binocular  vision  at  all  ordinary 
points,  combined  with  the  freedom  from  the  tensions  which  initiate 
the  deviations,  can  only  be  obtained  by  surgical  means. 

If  it  is  objected  that  the  orginal  conditions,  declinations,  ano- 
phoria,  katophoria,  or  hyperphoria,  those  conditions  from  which 
strabismus  usually  has  its  genesis,  are  normal  conditions,  and  that 
surgical  interference  with  normal'  though  unfavorable  conditions, 
which  are  very  common,  involves  risk  and  is  therefore  unwarranted, 
it  may  be  replied  that  the  dangers  attending  properly  executed  sur- 
gical corrections  of  strabismus  involve  no  more,  indeed  much  less, 
risk  than  attends  the  continued  existence  of  the  defects. 

SUKGICAL  TREATMENT  OF  STRABISMUS. 

The  location  and  extent  of  surgical  means  must  depend  on  the 
nature  and  degree  of  the  unfavorable  adjustments  which  give  rise  to 
the  deviations.  The  idea  that  a  deviation  toward  the  nose  makes  a 
lengthening  of  an  internus  or  the  shortening  of  an  externus  neces- 
sary, or  that  similar  direct  measures  are  demanded  in  case  of  an  out- 
ward deviation,  must,  if  we  are  to  proceed  by  rational  rather  than 
by  empirical  methods,  be  at  the  outset  abandoned. 

The  rule  which  should,  as  far  as  possible,  govern  all  operations 
for  strabismus  is  to  dispose  of  the  normal  anomalies  on  which  the 
squint  depends. 

These  anomalies  are  declinations,  anophoria,  katophoria,  and 
hyperphoria,  the  last  usually  depending  on  the  first.  Among  the 
people  of  Anglo-Saxon  lineage  katophoria  is  rarely  and  perhaps  never 
associated  with  converging  strabismus. 

These  then  are,  in  the  order  of  their  importance  in  a  given  case, 
the  conditions  to  be  met.  Of  these,  declination  stands  first,  yet,  un- 


SURGICAL  TREATMENT  OF  STRABISMUS. 


419 


fortunately.,  it  is  the  only  element  demanding  first  attention  which 
cannot  always  be  determined  or  which  can  be  determined  only  ap- 
proximately. Strabismics,  even  when  the  extent  of  deviation  is  small., 
often,  indeed  generally,  bring  one  and  then  the  other  eye  into  posi- 
tion for  fixation,  and  in  so  doing  correct,  with  the  last  fixing  eye, 
every  trace  of  declination.  Even  those  who  think  that  they  see  the 
images  simultaneously  in  fact  bring  one  and  then  the  other  eye  to 
bear  in  rapid  succession,  concealing  the  declination.  In  such  a  case 
the  declination  is  clearly  seen  if  the  small  black  points  of  soft  paper, 
mentioned  in  a  former  section,  be  applied,  one  at  the  inner  side  of 
the  cornea  on  the  conjunctiva,  the  other  at  the  temporal  side,  or  two 


Fig.  167. 


Fig.  168. 


-white  points  on  the  surface  of  the  cornea,  and  the  two  eye?  are  made 
alternately  to  come  into  fixation. 

The  principle  which  should  govern  in  a  case  may  be  thus 
stated  : — 

The  rational  treatment  in  a  case  of  strabismus  includes  only 
such  surgical  changes  as  would  have  been  justifiable  in  the  same  case 
could  the  conditions  have  been  discovered  before  the  period  ivlien  the 
squint  became  established. 

An  example  will  make  this  statement  more  clear. 

Above  are  seen  two  likenesses  from  photographs  of  the  same 
•child  at  different  periods  of  her  life.  Fig.  167  represents  the  child 
at  the  age  of  two  years.  In  this  figure  no  indication  of  squinting 
appears,  yet  each  of  the  brows,  especially  the  left  brow,  indicates  the 


420  ANOMALIES  OF  MOTOR  MUSCLES. 

effort  to  correct  anophoria  and  positive  declination  of  the  left  eye. 
Soon  after  this  photograph  was  taken  permanent  squint  was  estab- 
lished as  it  continued  and  is  seen  at  Fig.  168,  which  represents  the 
child  at  the  age  of  13,  when  she  came  under  treatment. 

At  this  time  there  was  an  extremely  pronounced  converging 
squint,  to  appearances  consisting  of  a  deviation  directly  in  of  the 
right  eye. 

There  were,  however,  found,  on  careful  examination,  enormous 
upward  rotations,  and  poor  downward  rotations.  If  a  card  were  in- 
terposed alternately  between  the  object  and  the  right  and  left  eye,. 
either  eye,  when  directing  the  line  of  regard  to  the  distant  object  after 
being  excluded,  moved  downward  as  well  as  outward.  This  down- 
ward movement,  when  either  eye  came  from  the  passive  state  of 
deviation  to  the  active  condition  of  fixation,  was  equal  to  about  20° 
of  prism.  The  right  eye  deviated  upward  more  than  the  left.  Both 
eyes  went  up  behind  the  card  with  a  twist,  returning  to  fixation  with 
an  equal  torsion. 

This  upward  tendency  of  both  e}res  was  then  an  original  condi- 
tion. It  did  not  commence  with  the  establishment  of  the  strabismus. 
It  was  in  itself  a  congenital  anomaly. 

The  treatment  was  directed,  not  to  the  conspicuous  defect,  but 
to  an  anomaly  which  actually  existed  when  the  first  photograph 
(Fig.  167)  was  taken  at  the  age  of  2  years.  That  is  to  say,  the 
tension  of  the  superior  rectus  of  each  eye  was  somewhat  relaxed,  but 
with  a  view  to  the  correction  of  the  twisting  at  the  same  time.  If 
the  reader  Avill  turn  to  page  400  a  copy  from  a  photograph  of  the 
same  child  will  be  seen  at  Fig.  158,  showing  the  apparent  result  dur- 
ing the  progress  of  this  treatment  while  yet  the  axes  of  the  two  eyes 
had  not  been  brought  quite  to  the  same  plane.  A  slight  squint  per- 
sisted which,  as  seen  by  the  companion  figure  (Fig.  159),  was  relieved 
by  a  prism  with  its  base  down.  A  further  stage  in  the  same  case  after 
a  further  tenotomy  of  the  right  superior  rectus,  there  was  single 
binocular  vision  at  all  ordinary  points  of  regard  and  a  perfect  free- 
dom of  movement  of  both  eyes  in  every  direction,  a  slight  hyperphoria 
with  an  associated  esophoria  remaining. 

The  details  of  this  case  have  been  thus  extensive^  related  with 
the  view  of  illustrating  and  emphasizing  the  principle  stated,  that 
the  rational  treatment  of  strabismus  should  deal  with  original  causes, 
causes  which  existed  before  the  development  of  the  squint. 

Since  the  study  of  the  influence  of  declinations  has  been  carried1 


THE  EMPIRICAL  METHOD.  421 

beyond  the  point  to  which  it  had  been  brought  at  the  time  of  the 
treatment  of  this  case,  it  has  become  evident  that  the  treatment  of 
anophoria  simply  is  not  in  most  cases  sufficient,  and  in  such  a  case 
as  that  just  related  much  may  now  be  accomplished  in  the  way  of 
correction  of  declinations. 

Tenotomies  of  the  superior  recti  of  sufficient  extent  to  fully 
correct  a  very  high  anotropia  are  operations  involving  great  risk  of 
inducing  a  tilting  of  the  meridians  and  are,  therefore,  notwithstand- 
ing the  satisfactory  result  of  some  such  cases,  to  be  avoided.  Slight 
relaxations  of  the  superior  recti,  involving  generally  not  more  than 
5°  or  6°,  may  be  done  in  these  extreme  cases,  provided  the  surgeon 
is  sure  of  the  pre-existing  declinations,  and  is  careful  to  work  toward 
their  elimination.  The  same  precaution  is  needed  in  cases  of  hyper- 
phoria.  In  exophoria  with  katophoria  tenotomy  of  the  inferior  recti 
is  an  operation  involving  great  risk,  and  is  better  avoided,  since  a 
contraction  of  the  superior  recti  can  be  done  instead. 

When  all  has  been  accomplished  by  .the  rational  method  that 
seems  practicable,  or  when,  in  the  absence  of  evidence  in  regard  to 
the  declinations  it  is  impossible  to  proceed  in  this  direction,  the  em- 
pirical method  may  be  resorted  to  for  a  part' of  the  work  only. 

The  principle  governing  all  the  operations  should  be  those  which 
are  described  for  heterophoria  and  declination.  In  no  case  should  a 
tendon  be  severed  from  the  eyeball  and  permitted  to  fall  back  with- 
out restraint. 

THE  EMPIRICAL  METHOD. 

In  a  considerable  proportion  of  cases  of  strabismus  no  tests  ex- 
cept those  which  can  be  made  by  the  tropometer  or  by  that  of  devia- 
tion in  exclusion  are  practical. 

In  such  cases,  after  such  measures  as  may  be  demanded  in  case 
of  anotropia  or  hypertropia  have  been  taken,  it  may  be  necessary  to 
bring  the  eyes  into  closer  relation  before  any  further  steps  in  what 
we  have  called  the  rational  method  can  be  taken.  It  is  then  neces- 
sary to  accept  the  empirical  method,  not  with  the  view  to  final  work, 
but  in  the  hope  of  obtaining  data  on  which  to  complete  the  work 
according  to  the  rational  method. 

In  a  case  of  converging  squint,  for  example,  with  amblyopia  of 
one  eye  and  a  persistent  refusal  to  recognize  diplopia,  we  may  do  a 
moderate  tenotomy  equally  for  each  internus,  not  by  any  means  suf- 
ficient to  correct  the  deviation  and  especially  not  to  the  extent  of 


422  ANOMALIES  OF  MOTOR  MUSCLES. 

impairing  the  inward  rotations  of  either  eye,  maintaining  at  least  a 
rotation  of  50°  to  the  medial  side.  Even  this  empirical  operation 
may  be  modified  to  a  certain  degree  by  observing  the  roll  of  the  eye 
when  the  bits  of  black  paper  are  applied  to  the  conjunctiva. 

By  such  means  the  strabismus  may  be  to  such  an  extent  modified 
that  proper  tests  can  be  made  and  the  further  correction  may  be  car- 
ried on  by  rational  methods. 

Again,  if  time  presses  and  a  correction  by  the  rational  method 
has  been  well  advanced,  it  may  be  excusable  to  adopt  the  empirical 
method  for  a  completion  of  the  case,  care  being  observed  to  divide 
the  relaxations  equally  between  the  eyes  and  to  preserve  full  rotation 
for  each. 

Of  course,  a  contraction  of  an  externus  for  converging  strabis- 
mus may  be  done  in  place  of  a  relaxation  of  an  internus,  and  con- 
versely, for  exotropia,  contraction  of  the  internus  is  in  almost  all 
cases  preferable  to  tenotomy  of  the  externus.  In  exotropia,  more- 
over, it  is  generally  safe  to  assume  a  positive  declination  of  each  eye, 
and  in  contracting  the  tendon  the  contraction  may  be  done  at  the 
superior  part  of  the  tendon,  thus  relieving  an  assumed  declination 
while  the  eyes  are  caused  to  approach. 

If  sufficient  time  is  given  to  the  treatment  of  a  case  of  con- 
verging strabismus  it  will  be  rare  that  occasion  will  require  a  ten- 
otomy of  either  internus  or  a  contraction  of  the  externus  beyond  a 
very  slight  modification,  which  may  be  required  for  finishing  the 
correction.  This  element  of  time  should  always,  when  possible,  be 
respected.  It  is  better  to  devote  several  months  to  the  rational  treat- 
ment of  such  a  defect  than  to  give  only  apparent  relief  by  adopting 
an  empirical  method. 

SECTION  LVI. 

RESULTS  OF  TREATMENT  OF  STRABISMUS. 

The  first  element  of  reliability  in  regard  to  the  reported  results 
of  strabismus  must  depend  upon  exact  methods  of  measuring  the  con- 
ditions with  which  we  are  dealing.  Many  authors  who  have  written 
on  strabismus  have  reported  results  which  could  scarcely  be  repeated 
by  the  same  methods  if  the  exact  conditions  before  and  after  such 
treatment  were  to  be  taken  fully  into  consideration,  as  they  might 
now  be  by  precise  methods  of  examination. 

To  assume  that  a  strabismus  is  cured  because  the  patient  looks 


RESULTS  OF  TREATMENT.  423 

less  "cross-eyed"  to  friends  is,  of  course,  wide  of  the  mark.  Scarcely 
less  crude,  however,  is  the  method  which  has  been  prevalent  of  asking 
the  patient  to  look  at  a  finger,  a  pencil,  etc.,  and  tell  whether  one  or 
two  images  of  the  object  can  be  seen. 

The  stereoscope  has  been  used  to  learn  whether  the  patient  can 
unite  the  pictures.  If,  for  example,  a  figure  representing  the  letter 
F  on  one  side  and  the  letter  L  on  the  other  can  be  so  united  as  to 
form  the  letter  E  it  has  been  supposed  that  the  presence  of  single 
vision  is  proved.  This  is  far  from  being  the  case.  The  stereoscope 
in  its  usual  form  contains  a  prism  of  about  7°  in  each  side,  in  all 
14°,  and  this,  with  a  convergence  equal  to  more  than  20°  of  prism, 
might  represent  a  converging  strabismus  still  remaining,  which, 
measured  at  twenty  feet,  would  require  prisms  equal  to  30°  to  cor- 
rect. But  this  is  not  all.  Many  persons,  especially  those  who  have 
a  moderate  strabismus,  acquire  a  faculty  of  uniting  mentally  the 
results  of  movements  of  the  eyes  which  are  not  exactly  simultaneous. 
Estimates  of  position  and  of  the  third  dimension  can  be  made  by 
these  people,  and  the  fact  that  they  see  two  such  figures  as  above 
referred  to  as  a  complete  letter,  of  which  these  two  are  elements,  is 
no  proof  under  these  circumstances  that  the  images  are  seen  simul- 
taneously. 

Bering's  test  in  case  of  persons  who  have  had  strabismus  may 
have  little  value  even  with  many  trials,  and  at  best  can  only  deter- 
mine the  fact  of  binocular  vision  without  indicating  its  difficulties. 
It  has  no  significance  when  the  questions  of  rotation,  heterophoria, 
or  other  moderate  disabilities  are  concerned. 

Tests  made  in  the  same  manner  as  in  cases  of  heterophoria  are 
by  far  more  reliable  than  all  others.  If  the  patient  cannot  locate 
the  images  with  the  phorometer  it  may  as  well  be  conceded  that  he 
has  not  binocular  single  vision. 


SECTION-  LVII. 

RESUME  OF  THE  OPERATIVE  TREATMENT   OF  STRABISMUS. 

We  may  arrange  and  condense  what  has  been  said  in  regard  to 
operative  treatment  so  as  to  present  a  comprehensive  view  in  a  few 
paragraphs. 

Let  it  be  assumed  that  the  case  in  hand  is  one  of  converging 
strabismus  of  rather  more  than  a  moderate  extent,  and  that  there  is 


424  ANOMALIES  OF  MOTOR  MUSCLES. 

ability  on  the  part  of  the  more  amblyopic  eye  to  see  and  to  form  a 
judgment  as  to  the  form  and  direction  of  a  well-defined  object,  as, 
for  example,  the  flame  of  a  candle. 

After  obtaining  a  general  history,  examining  with  the  ophthal- 
moscope and  determining  the  refraction,  the  tests  by  exclusion  are 
employed  as  those  most  likely  to  give  a  general  impression  of  the 
elements  of  the  defects. 

The  tropometer  is  then  brought  into  requisition  to  determine 
the  extent  of  the  rotations  in  different  directions.  The  upward  ro- 
tation is  likely  to  be  very  great  and  the  inward  rather  greater  than 
usual,  while  the  outward  rotation  is  somewhat  less  than  usual. 

An  attempt  is  then  to  be  made  to  determine  the  elements  of  the 
heterotropia  by  means  of  a  red  glass  and,  if  necessary,  prisms.  If  the 
patient  persists  in  his  opinion  that  he  can  see  only  one  image  after 
a  reasonable  trial  under  any  circumstances,  it  is  best,  after  the  next 
step  in  the  examination,  to  wait  a  day  for  further  examination.  The 
next  step  is  to  examine  by  the  clinoscope.  Some  patients  who  abso- 
lutely refuse  to  acknowledge  diplopia  will  recognize  the  two  pointers 
of  the  lens  clinoscope.  AYhen  this  can  be  done  an  important  step 
in  advance  has  been  taken.  Yet  it  is  to  be  remembered  (Section  LV) 
that  such  patients  often  appear  to  present  a  record  in  respect  to 
declination  much  more  correct  than  the  average  non-strabismic  per- 
son. This  apparent  correction  is  the  result  of  alternate,  though  per- 
haps very  rapidly  alternate,  fixation,  the  vertical  meridian  of  the 
eye  in  each  instance  adjusting  itself  accurately  to  the  vertical  posi- 
tion. Such  records  cannot  be  true.  And  whether  the  patient  sees 
in  this  way  or  fails  to  recognize  the  two  images  it  is  necessary  beyond 
all  things  to  form  at  least  an  approximate  estimate  of  the  directions 
of  the  declinations,  for  it  must  be  assumed,  not  only  that  there  are 
declinations,  but  very  important  ones.  If  the  clinoscope  or  lens 
clinoscope  gives  no  information,  resort  may  be  had  to  the  bits  of 
black  paper  on  the  surface  of  the  eye.  By  causing  the  eye  to  alter- 
nately fix  and  pass  into  the  squinting  position  the  direction  of  the 
leaning  of  the  meridian  may  be  determined. 

In  about  four  cases  out  of  five  with  converging  strabismus,  the 
right  meridian  will  be  found  to  lean  in  and  the  left  out  at  the  top. 

These  examinations  should  always  be  repeated,  if  possible,  on 
several  successive  days. 

Assuming  that  a  high  rotation  for  both  eyes  has  been  found, 
that  the  images  are  nearly  in  the  same  plane  and  that  there  is  a  nega- 


RESUME  OF  OPERATIVE  TREATMENT.  425 

tive  declination  of  one  eye  and  a  positive  declination,  of  the  other, 
the  first  step  in  the  operative  correction  may  be  taken  by  a  careful 
reduction  of  the  anophoria  by  a  graduated  tenotomy  of  the  superior 
rectus  of  each  eye,  the  dissection  of  the  insertion  of  the  tendon  being 
carried  to  the  nasal  side  of  the  tendon  of  the  eye  with  the  positive 
declination,  while  the  outer  border  is  carefully  preserved.  The  inner 
border  of  the  insertion  is  preserved  on  the  eye  with  negative  declina- 
tion. Both  may  be  done  at  one  sitting  or  on  different  days. 

If  this  step  has  been  taken  with  sufficient  care  some  modification 
of  the  strabismus  may  be  hoped  for,  but  if  there  is  still  doubt  as  to 
the  elements  of  the  defect,  a  carefully  graduated  tenotomy  of  each 
internus  may  be  resorted  to,  but  not  to  the  extent  of  a  correction  of 
the  squint.  Such  tenotomies  are  only  intended  to  enable  the  operator 
to  obtain  more  correct  data  by  which  to  complete  his  operations  with- 
out injury  to  the  rotating  ability  of  any  muscle,  and  with  the  final 
result  of  a  removal  of  the  underlying  conditions  which  induced  the 
esotropia. 

This  procedure  is  not  as  easy  as  it  is  to  look  at  a  squinting  eye, 
see  that  it  turns  in,  and  sever  an  internus  or  contract  an  externus 
muscle. 

Detail  of  procedure  must  be  varied  according  to  the  judgment  of 
the  surgeon.  The  important  principle  never  to  be  lost  sight  of  is  to 
induce  only  such  corrections  as  would  have  been  legitimate  had  the 
squint  never  occurred. 

It  is  a  complicated  and  difficult  procedure,  demanding  patience, 
time,  and  good  judgment.  But  it  has  its  reward  in  a  result  which 
is  more  than  a  cosmetic  improvement  of  rather  doubtful  quality.  It 
is  the  correct  procedure  if  it  is  not  the  rapid  one. 

I  venture  to  introduce  two  illustrations  from  photographs  of 
persons  who  have  been  subjected  to  the  standard  operations  for  con- 
verging squint,  an  operation  in  which  the  principles  which  I  have 
urged  are  disregarded.  These  are  fair  representations  of  a  very  large 
class,  not  necessarily  of  those  who  have  fallen  into  incompetent  hands, 
for  both  of  these  cases  were  patients  of  most  distinguished  surgeons, 
and  the  unfortunate  results  such  as  those  here  represented  are  found 
about  as  often  as  the  sequelae  of  operations  by  highly  trained  and  justly 
respected  surgeons,  as  of  operations  by  the  itinerant  oculist.  Such 
results  are  the  legitimate  consequences  of  the  standard  operation  for 
squint,  and  the  only  cause  of  surprise  at  the  effects  here  shown  is 
that  they  are  not  much  more  frequent  than  they  actually  are.  Many 


426 


ANOMALIES  OF  MOTOR  MUSCLES. 


cases,  however,  by  reason  of  the  enormous  declination,  retain  the 
tendency  to  squint  in,  as  the  case  shown  at  page  401,  notwithstand- 
ing the  great  disahilitv  induced  in  one  or  both  internal  recti. 


Fig.   Kit).  Fig.  170. 

Results  of  Over-correction  of  Converging  Strabismus. 


SECTION  LVIIT. 


"ANTIPATHY  TO  SINGLE  VISION." 

In  von  Graefe's  classical  description  of  the  condition  to  which 
he  applies  the  term  "Antipathy  to  Single  Vision,"  he  says :  "It  has 
sometimes  happened  to  me  that  after  squint  operations  with  appa- 
rently correctly  adjusted  visual  axes,  there  have  resulted  double 
images  only  slightly  removed  from  each  other.  The  visual  power 
of  each  eye  has  been  quite  good,  alternating  strabismus  having  pre- 
viously existed,  and  the  accommodative  power  has  been  similar  in  the 
two  eyes ;  nevertheless,  it  has  been  in  no  way  possible  to  bring  about 
single  vision. 'n 


1  "Es  ist  mir  namlich  einige  Male  naoh  Sohieloperationen  vorgekommen, 
dass  bie  ziemlich  richtiger  Einstellung  der  Sehaxen  sieh  cine  Diplopie  mit  wenig' 
distanten  Doppelbildem  zeigte.  Das  Sebvermogen  war  beiderseits  gleieh  gut, 
wie  aucb  alternirendes  Scbielen  vorangegangen  war,  auch  in  den  akkomoda- 
tiven  Verbiiltnissen  war  kein  Unterscbied  zwiseben  beiden  Augen  nachweisbar, 
dennoch  gelang  es  auf  keine  Weise,  Einfacbsehen  herbeizufiihren."  (Archiv. 
fiir  Ophthalmologie,  i,  1,  117.) 


ANTIPATHY  TO  SINGLE  VISION.  427 

He  remarks  that  this  condition  of  double  seeing  persists  not- 
withstanding the  interposition  of  prisms  in  various  positions,  and 
that  every  effort  of  the  patient  to  unite  the  images  results  only  in 
removing  them  to  still  greater  distances. 

He  adds :  "The  tendency  appears  to  be  a  direct  physiological 
contradiction.,  for  while  in  sound  eyes  some  approach,  especially  in 
case  of  large  retinal  pictures,  is  sufficient  to  induce  arbitrary  muscle 
contraction  in  the  interest  of  single  vision,  in  these  cases,  on  the 
other  hand,  it  is  found  that  exactly  the  opposite  condition  prevails, 
there  being  an  absolute  incompatibility  to  single  vision/'1 

In  a  still  later  article2  he  describes  the  condition  more  at  length, 
pointing  out  the  fact  that  the  double  images,  although  not  far  re- 
moved, pass  from  one  side  to  the  other  above  and  below  or  one  behind 
the  other,  always  on  the  point  of  uniting,  but  never  united.  Von 
Graefe  explains  the  anomaly  on  the  theory,  first,  of  injury  to  the 
nervous  centers,  and  second,  of  the  supposed  difficulty  of  obtaining 
regular  associated  action  between  muscles  which  have  long  been 
unused  to  association. 

A  careful  examination  of  these  cases  of  "antipathy  to  single 
vision"  leads  me  to  conclusions  widely  different  from  those  arrived 
at  by  von  Graefe. 

In  a  paper  read  before  the  American  Medical  Association,  June, 
1889,  I  expressed  my  disbelief  in  the  generally  accepted  view  of  the 
existence  of  a  physiological  antipathy  to  single  vision  and  my  con- 
viction that,  by  properly  selected  and  properly  executed  proceedings, 
this  unpleasant  condition  may  usually  be  eliminated. 

The  condition  of  antipathy  to  single  vision,  as  described  by  von 
Graefe  and  by  subsequent  authors,  depends  not  upon  lesion  of  the 
brain  or  faulty  projection  of  the  images  of  the  retina,  but  upon  non- 
corresponding  actions  of  the  muscles  under  the  influence  of  corre- 
sponding nerve  impulses  directed  to  them.  The  condition  is  entirely 
one  induced  by  the  operation,  and  in  most  individual  cases  it  can  be 
so  studied  that  the  reasons  for  the  loss  of  harmony  can  be  discovered. 

Without  giving  too  much  space  to  the  subject  it  may  be  briefly 


1  "Die   Tendenz   schien    hier   wirklich    eine   der   physiolo£rishen   diametral 
entgegengesitzte :     wahrend  bei  gesunden  Augen  nur  einege  Annahrung  beson- 
ders  bei  grossem  Netzhautbilde  genugt.  um   willkwiliche   Muskeikoutraktion 
in  Dienste  des  Einfaehsehens  hervorzurufen,  fand  in  diesen  Fallen,  als  wenn 
die  Augen  fur  das  Einfachsehen  platterdings  mit  einander  unvertragliclie  waren 
gerade  das  imgekehrte  Verhaltniss  statt.      (Archiv  fiir  Ophthalmologie,  i,   1, 
118). 

2  Arch,  fur  OphthaliKol.,  iii,  1. 


428  ANOMALIES  OF  MOTOR  MUSCLES. 

stated  that  such  antipathy  to  single  vision  rarely  occurs  except  when 
the  rotations  of  the  two  eyes  have  been  made  very  unequal  for  the 
two  eyes ;  and  again,  unless  by  the  operation  a  high  degree  of  acquired 
declination  has  been  induced,  no  such  antipathy  to  single  vision  will 
result.  It  follows  that,  in  order  to  relieve  the  patient  of  the  great 
annoyance  of  diplopia,  it  will  be  necessary  to  restore  comparative 
equality  of  action  for  the  two  interni  (or  extern!  if  they  are  the  dis- 
abled muscles),  and  at  the  same  time  any  leaning  of  the  images  must 
be  corrected. 

An  example  of  this  defect  and  a  study  of  its  elements  with  the 
progress  in  treatment  will  better  serve  to  point  out  the  principles  gov- 
erning the  existence  of  the  conditions,  the  examinations  required,  and 
the  course  of  treatment  than  a  long  discussion  of  these  conditions. 
(Page  401.) 

The  portraits  shown  at  Figs.  160,  1G1,  and  162  show  the  con- 
dition of  the  eyes  of  Miss  W.  when  she  consulted  me  in  January, 
1903. 

She  had  been  operated  on  some  years  before  for  converging  stra- 
bismus and  had  suffered  much  from  chorea  and  general  nervousness 
ever  since. 

Examinations  showed  that  she  was  using  glasses  s  -j-  3.50,  cyl 
-f-  .75,  axis:  E.  180,  L.  70,  and  that  with  these  there  was  diverging 
strabismus,  the  right  eye  turning  out,  the  left  habitually  in  fixation. 
"Removing  her  glasses,  converging  strabismus  at  once  occurred,  as 
shown  at  Fig.  160,  with  the  left  in  fixation,  the  right  turning  in.  The 
eyes  were  disagreeably  goggled  and  expressionless.  On  causing  the 
eyes  to  move  from  side  to  side  it  was  seen  that  the  right  cornea 
rotated  well  into  the  inner  canthus,  while  the  left  nasal  rotation 
showed  very  marked  restriction.  The  tropometer  showed  rotations: 
Right,  in  60°,  out  40°;  left,  in  28°,  out  60°;  up,  each  43°;  down, 
40°. 

She  had  diplopia  with  or  without  glasses,  homonymous  without, 
crossed  with  them  on,  but  if  she  fixed  the  right  eye  when  the  glasses 
were  off  the  diplopia  was  crossed,  while  if  the  same  eye  was  fixed 
when  the  glasses  were  in  place,  the  diplopia  was  homonymous.  Thus 
exactly  the  reverse  form  of  diplopia  occured,  depending  on  whether  the 
glasses  were  on  or  off. 

Looking  at  a  distant  point  of  light,  if  a  card  were  slipped  in 
front  of  the  fixing  eye  (either  right  or  left)  the  other  eye  moved 
distinctly  down  and  out  for  fixation,  the  downward  motion  being  as 


ANTIPATHY  TO  SINGLE  VISION.  429 

pronounced  as  the  other.  Xo  prisms  brought  the  images  into  closer 
relation  than  existed  without.  If  prisms  up  to  25°  base  out  were 
placed  before  the  eyes,  half  the  prisms  before  each  eye,  the  images 
remained  homonymous,  apparently  fifteen  inches  apart,  then  sud- 
denly passed  over  to  crossed  positions.  An  increase  or  decrease  of 
the  prism  induced  only  the  modification  in  the  character,  not  in  the 
degree  of  diplopia.  At  one  time  10°  left  hypertropia  was  shown,  the 
next  moment  an  equal  right  hypertropia  was  manifest. 

The  tests  by  the  lens  clinoscope  were  not  satisfactory,  but  ap- 
peared to  show  an  important  negative  declination  of  each  eye. 

With  certain  prisms  the  in  and  out  and  up  and  down  movements 
could  be  considerably  neutralized  in  the  test  for  deviation  in  exclu- 
sion ;  then  an  axial  rotation  was  much  more  apparent  than  at  other 
times. 

In  order  to  bring  about  a  relation  of  the  eyes  in  which  some 
more  definite  tests  could  be  made,  on  the  third  visit  an  advancement 
of  the  internus  of  the  left  eye  (the  tendon  which  had  been  severed) 
was  done.  After  a  few  days  the  nasal  rotation  of  that  eye  had  greatly 
improved.  It  then  appeared  that  there  was  decided  negative  declina- 
tion (5°  or  more  or  less)  of  the  right  eye  and  slight  positive  declina- 
tion of  the  left.  These  tests  were  too  uncertain  to  be  fully  relied 
on,  but  a  moderate  change  in  the  direction  of  the  insertion  of  the 
superior  rectus,  right  eye,  brought  about  a  marked  improvement  in 
the  appearance  of  the  eyes  and  images  could  be  for  a  short  time 
united. 

After  a  few  days  still  further  correction  for  declination  was 
obtained,  after  which  the  images  could  be  held  indefinitely  in  union. 

The  experience  related  above  is  not  exceptional ;  indeed,  it  is 
common,  and  the  results  may  be  summed  up  in  the  statement  that 
the  lateral  rotations  have  been  rendered  disproportionate  and  the 
effects  of  declination  increased  as  a  result  of  operations.  The  rem- 
edy consists  in  equalizing  the  rotations  and  in  reducing  the  declina- 
tions. 

In  concluding  this  section  it  seems  desirable  to  add  some  para- 
graphs taken  from  an  article  contributed  by  me  to  Archives  of  Oph- 
thalmology in  1891. a  Although  the  views  of  the  causes  of  the  an- 
tipathy to  single  vision  have  been  materially  modified  during  the 
fourteen  years  since  the  appearance  of  that  article,  since  they  have 


1  Archives  of  Ophthalmology,  vol.  xx,  No.  3,  1891. 


430  ANOMALIES  OF  MOTOR  MUSCLES. 

been  studied  in  connection  with  declinations  and  the  conditions  re- 
vealed by  the  tropometer,  as  well  as  with  those  conditions  recognized 
at  the  time  of  writing,  the  facts  exhibited  are  so  interesting  that  I 
am  induced  to  transcribe  them  without  change.  The  reader  who  has 
become  familiar  with  the  principles  discussed  in  the  preceding  sec- 
tions will  be  prepared  to  modify  the  conclusions  according  to  the 
more  recent  observations  of  facts. 

A  causative  influence,  and  one  which  acts  as  an  element  in  nearly 
all  of  these  cases,  is  the  difference  in  relative  tension  of  muscles  which 
act  in  the  vertical  direction. 

We  have  seen  that  the  influence  inducing  hyperphoria  is  often, 
if  not  always,  in  the  character  of  declinations,  and  where  in  the  fol- 
lowing few  pages  to  hyperphoria  are  attributed  certain  peculiarities 
of  action,  it  will  be  observed  that  the  condition  underlying  the  hyper- 
phoria may  even  more  effectually  explain  these  peculiarities. 

"The  instinct  of  bringing  images  to  the  same  horizontal  plane 
appears  to  be  very  great  and  only  second,  if  indeed  it  is  second,  to 
that  of  union  of  images.  In  case  of  double  images,  whatever  the 
difficulty  of  blending  may  be,  the  patient  instinctively  exerts  his 
best  endeavors  to  place  the  images  in  the  same  horizontal  plane.  It 
thus  happens,  that  in  certain  cases  in  which,  either  with  or  without 
slight  lateral  inequality  of  tension,  the  effort  to  bring  images  to  the 
same  plane  induces  a  lateral  squint, — a  squint  which  may  be  variable; 
that  is,  such  a  squint  may  at  one  period  of  life  be  converging,  and  at 
another  diverging.  Thus,  in  a  case  now  under  my  observation,  the 
patient  was,  during  her  childhood,  subject  to  a  very  pronounced  con- 
verging squint.  During  the  past  twenty  years  she  has  had  conspicu- 
ous diverging  squint,  although  no  operation  has  been  done.  Such  a 
condition  may  properly  be  called  variable  strabismus,  its  character 
of  divergence  or  convergence  changing  from  time  to  time,  remaining 
possibly  in  one  direction  during  several  years,  then  changing  to  the 
opposite  direction. 

"If  in  such  a  case  one  or  both  interni  or  externi  are  cut,  double 
vision  of  an  intractable  form  is  likely  to  result.  In  such  cases  we 
must  make  diligent  search  for  the  vertical  deviation,  a  condition  often 
obscure  or  not  at  all  manifest,  before  we  can  succeed  in  establishing 
binocular  vision. 

"I  have  had  the  good  fortune  to  obtain  a  daguerreotype  por- 
trait of  the  lady  whose  case  has  just  been  mentioned,  taken  dur- 
ing her  childhood.  (Fig.  171.)  The  picture  shows  converging 


ANTIPATHY  TO  SINGLE  VISION. 


431 


squint,  so  pronounced  that  few  ophthalmic  surgeons  even  at  the 
present  day  would  hesitate  in  regarding  it  as  a  proper  case  for  a 
free  division  of  the  internus  of  one,  if  not  of  hoth  eyes.  Had  such 
an  operation  heen  performed  upon  this  patient  in  early  life,  intrac- 
table diplopia  would  doubtless  have  resulted,  and  eventually  extreme 


Fig.   171. — A  Case  of  Converging  Strabismus  which   Changed   to 
Diverging  Strabismus  in  Later  Life. 

diverging  strabismus.  In  another,  photographic,  portrait  of  this  lady, 
made  by  myself  a  few  years  ago  (Fig.  172),  a  moderate  appearance 
of  diverging  strabismus  is  seen.  In  fact  a  divergence  of  more  than  12° 
with  corresponding  crossed  diplopia  existed.  But  the  most  striking 


Fig.  172. — Slight  Diverging  Strabismus  Succeeding  the 
Convergence  Seen  at  Fig.  171. 

feature  suggested  by  this  photograph  is  the  left  hypertropia,  well 
defined  in  the  position  of  the  eyes  and  of  the  brows.  The  question 
at  once  arises  whether  the  change  from  converging  to  diverging 
strabismus  is  not  the  result  of  some  radical  change  in  the  static  con- 
dition of  the  eye-muscles.  That  this  is  not  the  case  will  be  seen  by 


432  ANOMALIES  OF  MOTOR  MUSCLES. 

the  most  cursory  glance  at  the  third  portrait  (Fig.  173),  in  which 
the  old  converging  squint  has  returned.  This  condition  of  con- 
vergence can  be  induced  at  any  time  by  the  application  of  a  solution 
of  atropine  to  the  eyes.  At  the  time  of  taking  this  third  portrait, 
atropine  had  been  applied  twice  a  day  for  three  successive  days,  and 
its  effects  were  complete.  A  week  after  that  time  the  diverging  squint 
had  returned  and  has  continued  during  the  year.  The  transformation 
from  divergence  to  convergence  occurs  within  an  hour  after  the  first 
application  of  the  atropine,  and  the  present  habitual  condition  of 
divergence  returns  as  soon  as  the  effect  of  the  drug  passes  off.  This 
variableness  is,  without  doubt,  due  to  the  action  of  the  muscles  in 
the  effort  to  overcome  the  unequal  height  of  the  images,  and  until 


Fig.    173. — Diverging   Strabismus   Converted   into  the  Converging 
Form  by  the  Instillation  of  Atropine. 

the  condition  of  the  hypertropia  is  eliminated  such  changes  of  the 
lateral  relations  are  liable  to  occur.1  In  passing,  a  single  thought  may 
be  given  to  the  adverse  testimony  of  such  cases  to  the  well-known 
doctrine  of  the  relations  between  the  excessive  efforts  at  accommoda- 
tion and  converging  strabismus;  for  here  the  converging  strabismus 
occurs  only  when  accommodation  is  neutralized.  The  present  interest 
in  the  case  centers  in  the  fact  that  had  a  free  tenotomy  of  an  internus 
been  practiced  during  childhood,  the  almost  certain  result  would  have 
been  an  "antipathy  to  single  vision."  Even  at  the  present  time,  when 
the  conditions  of  hyperphoria  and  hypertropia  are  carefully  sought 
for,  this  patient  is  able,  under  many  circumstances,  to  conceal  com- 
pletely the  evidence  of  hyperphoria  as  shown  by  the  phorometer. 

"A  curious  fact  in  connection  with  the  inequality  of  tension  of 


1  The  reader  must  remember  that  at  the  time  at  which  this  was  written 
the  influence  of  declinations  had  not  been  studied,  and  what  is  here  attributed 
to  hyperphoria  might  better  be  explained  by  considering  that  in  one  condition 
of  deviation  a  +  and  in  the  other  a  —  declination  was  being  corrected. 


ANTIPATHY  TO  SINGLE  VISION.  433 

the  lateral  muscles  associated  with  hyperphoria  is  that  a  condition 
which  in  a  passive  state  of  the  muscles  of  either  eye  or  of  both  eyes 
is  a  marked  divergence.,  becomes,  as  soon  as  all  the  muscles  are  en- 
gaged in  the  act  of  adjustment,  pronounced  convergence  attended 
by  homonymous  diplopia.  Conversely,  a  like  change  may  occur  when 
the  tendency  is,  in  the  passive  state,  to  converge. 

"A  very  practical  illustration  of  what  has  been  stated  may  be 
found  in  an  actual  history  which  I  condense  for  this  purpose.  In  a 
child  with  left  hyperphoria  (or  hypertropia)  the  left  eye  drifted  out- 
ward during  the  first  few  years  of  life.  (Such  a  diverging  squint 
is  rarely  observed  by  parents  unless  it  is  extreme.)  At  length,  pre- 


Fig.  174. — Diverging  Strabismus  which  in  Youth  Became  Marked 
Converging  Squint. 

sumably  as  the  result  of  a  change  in  the  methods  of  making  the  efforts 
to  adjust  for  the  horizontal  plane,  the  squint  became  convergent. 
The  appearance  of  the  eyes  of  this  patient  in  early  childhood  is  rep- 
resented in  Fig.  174,  which  is  copied  and  enlarged  from  a  daguerreo- 
type picture  of  him  taken  at  the  age  of  about  three  years. 

"About  three  or  four  years  later,  and  after  the  divergence  had 
given  place  to  convergence,  a  surgeon  performed  tenotomies  of  the 
two  recti  interni,  presumably  severing  both  tendons  completely.  The 
result  proving  an  over-correction,  the  effect  of  the  operation  on  one 
eye  was  modified  by  the  insertion  of  a  (conjunctival?)  suture.  The 
result,  in  view  of  what  has  been  stated  above,  was  such  as  we  might 
anticipate.  Double  vision  of  the  most  annoying  character  was  always 
present.  The  efforts  of  many  distinguished  surgeons  to  induce  these 
twin  images  to  unite  by  means  of  prisms,  even  for  an  instant,  were 
fruitless  after  trials  repeated  during  many  years.  The  case  found  a 


434  ANOMALIES  OF  MOTOR  MUSCLES. 

prominent  place  in  ophthalmological  literature,  endorsed  by  several 
distinguished  surgeons,  as  one  of  the  class  now  under  discussion.  No 
case  could  therefore  afford  us  a  better  model  for  our  study. 

"It  proved  easier  for  this  patient  to  fix  objects  with  the  left  eye. 
That  being  the  case,  we  may  suppose  that  he  would  make  a  certain 
effort  of  adjustment  with  the  weakened  internus  of  that  eye,  which 
would  1)0  associated  with  a  corresponding  excessive  effort  of  the  op- 
posite internus.  But  these  unequal  efforts  would  also  be  combined 
with  the  effort  to  adjust  for  the  difference  in  the  positions  of  the 
images  with  reference  to  the  horizontal  plane.  The  result  would  be 
an  excessive  rotation  of  the  right  eye  to  the  nasal  side  with  homony- 
mous  double  images.  If,  on  the  other  hand,  a  patient  with  this  com- 
bination of  defects  should  look  at  an  object  which  is  isolated  from 
other  objects  which  may  serve  to  aid  the  disabled  eye  in  active  ad- 
justment, as,  for  instance,  at  a  church  spire,  or  at  the  moon,  or  a 
bright  star,  in  which  cases  only  the  clear  sky  is  in  immediate  relation 
to  the  object,  the  most  disabled  eye  would  at  once  drift  outward,  and 
crossed  diplopia  would  result.  So  also,  if  a  small  screen  were  to  be 
interposed  between  either  eye  and  the  object  looked  at,  thus  shutting 
it  out  from  active  participation  in  the  'effort  of  adjustment,  the  cov- 
ered eye  would  diverge  in  a  marked  manner  and  would  move  inward, 
perhaps  to  the  extent  of  one-third  the  diameter  of  the  cornea,  as  soon 
as  the  screen  should  bo  removed,  and  then  homonymous  diplopia 
Mould  be  observed.  Or  again,  if  the  subject  of  such  defect  were  to 
look  through  a  grating,  as,  for  instance,  through  the  palings  of  a 
picket  fence,  an  object  seen  beyond  the  fence  would  be  seen  doubled, 
and  the  diplopia  would  be  crossed;  while  an  object  seen  between  the 
person  and  the  fence  would  be  double  also,  but  the  double  images 
would  be  homonymous.  In  the  first  instance,  looking  beyond  the 
fence,  the  adjusting  energy  of  one  eye  becomes  passive,  as  in  the  case 
of  looking  at  the  object  against  the  clear  sky,  with  resulting  crossed 
diplopia.  In  the  other  instance,  looking  at  the  object  nearer  than 
the  fence,  active  adjustment  of  both  eyes  occurs  with  excessive  con- 
vergence and  homonymous  double  images.  All  these  suppositions  and 
conclusions  have  been  fully  justified  in  the  actual  treatment  of  these 
cases. 

"In  certain  cases  in  which  this  intractable  diplopia  exists,  the 
patient  has  the  extraordinary  faculty  of  selecting  at  will  which  eye 
shall  fix  the  object,  and  the  diplopia  becomes  homonymous  or  crossed, 
according  as  the  one  or  the  other  eye  is  engaged  in  direct  fixation. 


ANTIPATHY  TO  SINGLE  VISION.  435 

Thus,  in  the  case  of  a  lady  patient,  if  I  direct  her  to  look  with  the 
right  eye,  I  can  see  that  the  eyes  are  strongly  converged,  and  she 
reports  the  presence  of  homonymous  double  images.  If  I  then  direct 
her  to  look  with  the  left  eye,  the  change  may  require  a  few  seconds 
or  it  may  take  place  very  quickly.  Then  the  eyes  are  plainly  seen 
to  diverge,  and  the  diplopia  is  crossed.  In  such  a  case,  the  nervous 
impulse  directed  to  the  right  internus  is  greater  than  the  normal 
during  fixation  with  that  eye,  and  when  a  corresponding  impulse  is 
sent  to  the  left  internus,  the  eye  is  caused  to  swing  in  excessively  and 
too  great  convergence  results.  On  the  contrary,  when  the  left  eye  is 
fixed,  there  is  no  such  excess  of  nervous  impulse  sent  to  the  left 
internus,  and  as  no  excessive  impulse  is  therefore  sent  to  the  right 
internus,  that  eye  swings  outward  passively,  and  crossing  of  images 
results.  But  in  this  explanation  we  must  not  lose  sight  of  the  im- 
portant, probably  the  most  important,  element  in  the  causation  of 
the  inward  swing  in  many  if  not  in  the  majority  of  cases.  This  is 
the  influence  of  the  difference  of  tension  of  the  muscles  which  move 
the  eyes  in  the  vertical  direction.  This  influence  is  often  sufficient, 
even  though  the  moving  power  of  the  corresponding  lateral  muscles 
should  be  equal,  to  cause  a  swing  beyond  that  which  would  result 
from  a  given  impulse  to  a  lateral  muscle.  I  have  rarely  met  with  a 
case  of  the  so-called  "antipathy  to  single  vision"  in  which  this  element 
did  not  play  an  important  role. 

"It  needs  no  argument  to  show  that  the  defect  which  causes  the 
patient  to  have  homonymous  diplopia  when  looking  at  an  object,  say 
at  twenty  feet  distance,  and  heteronymous  diplopia  when  looking  at 
the  same  object,  if  a  grating,  like  the  fence  of  which  we  have  spoken, 
is  interposed  between  the  eyes  and  the  object,  or  which  causes  the 
same  patient  to  have  homonymous  images  when  looking  at  an  object 
isolated  from  visible  surroundings,  lies  neither  in  the  brain  nor  in 
faulty  projection  from  the  retinae,  but  in  peculiar,  although  perhaps 
obscure,  defects  in  the  adjusting  apparatus. 

"Homonymous  diplopia  caused  by  a  brain  defect  or  a  retinal 
defect  would  remain  homonymous  under  all  the  circumstances  which 
have  just  been  mentioned.  Activity  or  passivity  of  certain  efforts  of 
adjustment  could  and  would  be  modified  by  the  circumstances  men- 
tioned, and  the  phenomena  resulting,  which  at  first  appear  confused 
and  irregular,  are  in  reality  uniform  and  in  accordance  with  fixed 
laws/' 


436  ANOMALIES  OF  MOTOR  MUSCLES. 

SECTION  LIX. 
THIRD  DIVISION. 

Class  IV. 
NYSTAGMUS.1      TALANTROPIA.2 

The  terra  nystagmus,  as  used  in  ophthalmology,  is  applied  not 
only  to  the  involuntary  oscillations  of  the  globe  of  the  eye  which  are 
habitual  and,  in  waking  hours,  constant  with  some  persons  in  health, 
and  which  continue  in  most  cases  for  a  lifetime,  but  to  the  spasmodic 
twitchings  which  are  the  result  of  disease  of  the  brain  cortex.  Neither 
the  nature  of  the  affections  nor  their  manifestations  are  alike,  yet 
the  same  term  has  been  applied  to  both. 

Considering  this  fact,  and  in  view  of  the  advantage  of  placing 
each  of  these  forms  of  ocular  affection  in  its  own  appropriate  rela- 
tions to  other  motile  irregularities,  no  excuse  would  seem  to  be  re- 
quired for  the  introduction  of  a  new  term  for  one  of  the  affections. 
Since  the  system  of  classification  adopted  in  this  work  is  best  served 
by  applying  the  new  term  to  the  functional  form.,  I  have  suggested 
one  which  is  at  least  as  appropriate  as  the  one  in  common  use. 

The  term  talantropia,  then,  is  proposed  to  be  applied  to  invol- 
untary oscillations  of  the  globe  of  the  eye  not  depending  on  cortical 
lesions,  whether  from  side  to  side,  in  a  vertical  direction  or  about  the 
antero-posterior  axis  of  the  eye. 

The  term  talantropia,  according  to  this  suggestion,  signifies  an 
oscillating  turning  of  the  eye  as  distinguished  from  the  twitching 
side  to  side  movements  of  the  eyes  from  cortical  disease  or  pressure. 

In  certain  particulars  these  talantropic  oscillations  are  alike. 
They  are  generally  constant  when  the  eyes  are  in  fixation,  they  in- 
crease with  an  increase  of  the  effort  at  fixation,  and  they  are  greater 
when  the  eyes  are  turned  in  certain  directions  than  when  they  are 
directed  in  others.  In  sleep  they  disappear. 

While  talantropic  nystagmus  is  not  in  itself  a  disease,  it  is  often 
the  result  of  disease,  and  in  almost  every  instance  of  long  standing  is 
associated  with  marked  reduction  of  visual  power. 

The  osci^atory  movements  are,  the  to  and  fro  movements  from 


1  From  vevvrdfrv,  to  nod  in  sleep. 

2  From  ToXdirwSts,  an  oscillating. 


TALANTKOPIA.  437 

side  to  side,  the  horizontal  nystagmus  or  horizontal  talantropia;  the 
rotatory  movements  about  the  optic  axis,  rotatory  nystagmus;  and 
the  movements  nearly  in  a  vertical  direction,  vertical  nystagmus,  a 
less  common  form  than  the  others,  but  especially  noticeable  among 
miners. 

There  are  also  many  cases  in  which  the  vertical  or  the  horizontal 
oscillations  are  mixed  with  the  rotatory  movements,  and  occasionally 
the  horizontal  and  vertical  forms  combine  as  an  oblique  form. 

Xeither  the  vertical  nor  the  horizontal  varieties  are  often  seen 
as  pure  forms,  cases  being  much  more  frequently  of  a  mixed  char- 
acter. In  both  of  these  mixed  forms,  however,  the  horizontal  or  the 
vertical  oscillations  are  often  so  conspicuously  predominant  that  the 
rotatory  movement,  which  complicates  many  cases,  is  with  difficulty 
recognized. 

The  movements  are  usually  quite  rhythmic,  though  not  for  con- 
siderable periods  of  time  uniformly  so.  If  the  gaze  is  indifferently 
fixed,  the  ram'dity  of  the  oscillations  and  their  extent  may  be  much 
less  than  when  the  attention  is  definitely  fixed  upon  an  object.  On 
the  whole,  the  rapidity  of  movements  is,  within  limits,  in  some  de- 
gree uniform  in  the  same  individual.  If  the  excursions  are  long  and 
the  oscillations  comparatively  slow  they  do  not  often  in  this  indi- 
vidual case  rise  to  extremely  short  and  rapid  movements. 

However  slow  the  movements  may  appear  or  however  slight  by 
ordinary  inspection,  when  the  eye  is  examined  by  the  ophthalmo- 
scope it  appears  to  move  with  immense  rapidity  and  to  a  great  extent. 

The  oscillations  are,  in  by  far  the  greatest  number  of  cases,  com- 
mon to  the  two  eyes,  yet  cases  occur  in  which  only  one  eye  is  affected. 

Nettieship1  mentions  three  brothers  (children)  all  of  whom 
had  unilateral  nystagmus,  and  of  whom  two  had  fits  and  strabismus. 

In  another  case,  an  infant,  there  was  unilateral  nystagmus  with 
rhythmical  movements  of  the  head  and  the  corresponding  arm. 

Soelberg  Wells2  a1  so  mentions  a  case  of  vertical  nystagmus  ("the 
only  case  of  vertical  oscillation  with  which  he  had  ever  met"),  which 
was  confined  to  one  eye. 

While  objects  are  seen  in  their  appropriate  form  by  those  who 
have  binocular  single  vision,  the  form  of  the  object  appears  to  un- 


1  Ophthalmic  Hospital  Reports,  xi,  p.  75. 

2  "Treatise  on  the  Diseases  of  the  Eye,"  p.  569.     Zehender  also  describes 
a  case  of  unilateral  nystagmus  in  a  child   (Klinische  Monatsblatter,  1870,  p. 
112). 


438  ANOMALIES  OF  MOTOR  MUSCLES. 

dergo  a  change  when  the  images  are  separated,  as  they  may  be  with 
a  prism.  In  that  case  the  image  of  a  candle  flame.,  for  example,  is 
with  the  horizontal  variety,  very  markedly  broadened,  while  in  the 
rotatory  form  it  is  enlarged  in  all  directions.  This  fact  is  sometimes 
helpful  in  determining  the  special  form  of  the  oscillation  in  the  two 
eyes,  and  Alfred  Graef'e  has  reported  a  case  in  which  by  this  means 
he  was  able  to  demonstrate  the  existence  of  the  vertical  form  in  one 
eye  and  the  horizontal  in  the  other.1 

Other  cases  have  been  reported  in  which  quite  anomalous  forms 
of  oscillation  have  been  observed.2 

The  affection  may  commence  very  early  in  life,  so  early  as  to 
be  observed  as  soon  as  the  child  begins  to  look  about.  Such  cases  are 
usually,  though  it  appears  to  me  with  too  little  reason,  regarded  as 
congenital.  Other  cases  are  acquired  later  in  life.  This  is  especially 
the  case  with  the  nystagmus  of  miners,  with  the  nystagmus  of  paral- 
ysis, and  with  some  cases  of  the  nystagmus  of  disseminated  myelitis. 

The  case  of  Xettleship,  in  which  there  was,  associated  with  the 
movements  of  the  eyes,  rhythmic  movements  of  the  head  and  arm, 
is  an  example  of  a  form  of  the  affection  not  very  rare.  The  associa- 
tion also  of  epileptic  and  other  important  nervous  troubles  is  'not 
uncommon. 

Apparent  movement  of  objects  corresponding  to  the  movements 
of  the  eyes,  while  not  common,  have  been  observed  from  time  to  time. 

A.  V.  Reuss3  reports  two  such  instances,  both  in  young  children, 
in  which  the  subjective  movements  of  objects  corresponded  closely 
with  the  swing  of  the  eyes.  Snell4  also  mentions  the  case  of  an  ac- 
quired nystagmus,  to  which  reference  will  again  be  made,  in  which 
objects  appeared  to  move  up  and  down.  Such  subjective  movements 
are  also  sometimes  observed  in  the  nystagmus  of  miners. 

I  have  met  with  a  number  of  cases  of  albinism  associated  with 
talantropia,  and,  indeed,  nystagmus  may  be  regarded  as  a  nearly  con- 
stant attendant  on  albinism.  The  affection  is  often  associated  with 
microphthalmus  and  other  degenerate  forms  of  the  eyes. 

Talantropia  is  not  unfrequently  found  in  connection  with  con- 


1  Graefe  und  Saemisch:     "Handbueh.''  vi,  1. 

2  In  the  British  Medical  Journal,  1892,  J.  D.  Bell,  W.  T.  Conkling,  J.  Court, 
H.  B.  Hewitson,  Simeon  Snell,  and  G.  W.  Thomson  discuss  nystagmus,  their 
contributions  indicating1  a.  considerable  diversity  of  opinion. 

3  Centralblatt  fur  Prak.  Augenheilkunde,  March,  1881. 

4  "Transactions  of  the  Ophthalmological  Society  of  the  United  Kingdom," 
1891. 


TALANTROPIA.  439 

genital  cataract,  leucoma  from  early  life,  pigmentary  retinitis  with 
central  scotoma,  and  other  lesions  of  the  media  occurring  at  a  very 
early  age. 

In  most  cases  of  paralysis  of  the  eye  muscles  there  exists  a  tem- 
porary oscillation  when  the  attempt  is  made  to  turn  the  eye  in  the 
direction  of  the  affected  muscle. 

Conspicuous  among  the  diseases  of  the  nervous  centers  in  whicli 
nystagmus  plays  an  important  role  is  the  disease  known  as  dissemi- 
nated nodular  sclerosis  (sclerose  en  plaques).  This  disease,  which  is 
peculiar  to  young  persons,  was  first  described  by  Charcet  and  Vulpian 
in  1866.  It  is  characterized  by  a  tremor  which  comes  on  with  an 
intended  movement  and  increases  as  the  movement,  for  example,  of 
the  arm  or  hand,  becomes  more  and  more  specialized. 

A  tremor  of  the  eyes,  a  nystagmus,  increasing  with  efforts  at 
fixation,  is  one  of  the  conspicuous  and  almost  constant  symptoms  of 
the  disease,  although  cases  have  occurred  in  which  the  tremor  of  the 
eyes  has  been  absent.  It  is  also  sometimes  an  accompaniment  of  hys- 
teria.1 

Talantropia  may  occur  in  several  members  of  one  family.  In 
1880  three  members  of  one  family,  a  brother  and  two  sisters,  who 
were  under  my  care,  were  subjects  of  the  affection,  and  I  saw  two 
young  cousins  of  these,  a  boy  and  a  girl,  who  were  also  affected  in 
like  manner.  In  all  these  five  cases  there  was  a  high  degree  of  astig- 
matism, but  the  oscillation  of  the  eyes  is  in  only  a  moderate  per  cent. 
of  cases  associated  with  pronounced  astigmatism. 

Cases  of  talantropia  acquired  in  adult  age  are  more  instructive 
in  respect  to  the  origin  and  nature  of  the  affection  than  those  which 
occur  in  the  first  years  of  life. 

In  the  most  of  these  acquired  cases  the  trouble  has  arisen  as  the 
result  of  prolonged  and  strenuous  effort  directed  to  the  elevator  mus- 
cles of  the  eyes. 

Dr.  Simeon  Snell  reports2  an  interesting  case  of  acquired  nys- 
tagmus in  the  person  of  a  compositor.  The  trouble  had  only  been 
observed  a  few  days  when  the  patient  first  consulted  Dr.  Snell.  He 
had  retired  at  night  apparently  well,  and  on  rising  in  the  morning 
saw  all  surrounding  objects  moving  vertically.  The  movements  of 
oscillation  were,  like  the  subjective  movements,  vertical  and  extremely 
rapid. 


1  Dr.  J.  Santos  Fernandio,  Havana. 

2  "Ophthalmic  Society  of  the  United  Kingdom  Report  for  1891." 


440  ANOMALIES  OF  MOTOR  MUSCLES. 

Dr.  Snell  visited  the  rooms  where  the  patient  was  accustomed 
to  work  and  found  them  well  lighted.  He  observed  that  the  man 
was  accustomed  to  look  strongly  upward  at  his  copy  instead  of  raising 
the  head. 

There  was  improvement  after  a  few  days  of  rest. 

Among  the  various  avocations  probably  none  in  which  large 
numbers  of  men  are  employed  demand  from  the  men  so  great  strain 
on  the  elevator  muscles  of  the  eyes,  under  unfavorable  conditions,  as 
does  that  of  operating  in  coal  mines.  Hence,  in  recent  years  much 
interest  has  been  aroused  in  what  is  known  as  the  "nystagmus  of 
miners." 

Nicden1  stated  in  1881  that  he  had  examined  7416  miners  and 
that  he  had  found  nystagmus  299  times  or  4.3  per  cent,  of  the  whole. 
This  large  per  cent,  he  had  found  only  in  certain  mines  where  the 
conditions  of  light  and  space  were  extremely  bad. 

Deconde  was  the  first  to  mention  the  affection  in  connection  with 
miners,2  but  he  mentioned  only  two  cases.  Alfred  Graefe,3  in  1875, 
mentions  three  cases,  and  Xeiden,4  Xoel,5  and  others  soon  added  to 
the  lists. 

Dr.  Dransart6  was  able  to  collect  12  cases  from  the  miners  of 
Anzin,  and  he  has  given  an  excellent  account  of  the  affection. 

He  concludes  that  the  nystagmus  of  miners  is  the  result  of  a 
myopathy  of  the  elevator  muscles  of  the  eyes  (the  superior  recti,  the 
inferior  oblique,  and  he  adds,  the  internal  rectus),  being  related  more 
or  less  intimately  with  the  anasmia  induced  by  the  environments  of 
the  miners,  and  with  the  paresis  of  accommodation. 

The  motions  of  this  nystagmus  are  both  horizontal  and  vertical. 

According  to  Dransart,  when  the  eyes  are  directed  down  the 
oscillations  disappear  and  the  eyes  seem  normal. 

The  nystagmus  only  occurs  when  the  line  of  regard  is  directed 
above  the  horizontal  plane. 

The  introduction  then,  according  to  this  author,  into  the  field  of 
action  of  the  group  of  elevators  of  the  eyes,  is  the  efficient  cause  of 
the  oscillations.  Other  conditions  cease  to  act  as  soon  as  this  direc- 
tion of  the  eyes  above  the  plane  of  the  horizon  is  discontinued. 


1  "Proceedings    of    the    International    Medical    Congress,"    London,    1881, 
vol.   Hi,  p.  89. 

2  Deconde,  in  Arch.  Belg.  de  Med.  Mil.,  1861.     T.  27,  p.  337. 
8  Graefe  und  Saemisch:      "Handbuch." 

4  Berlin.  Klin.  Wochens.,  1874. 

5  An.  d'Oculist.,  1874. 

•An.  d'Oculist.,  September,  1887. 


TALANTROPIA.  441 

Alfred  Graefe  also  speaks  of  the  increase  of  the  oscillations  when 
his  patients  looked  up. 

If  the  circumstances  under  which  the  miners  work  are  consid- 
ered, the  facts  related  by  these  authors  are  explained. 

Walking  in  the  mines  often  requires  the  miners  to  stoop,  as  the 
walls  are  low.  This  causes  them  to  look  up  from  the  brows.  At  their 
work  also  they  are  forced  not  only  to  look  up  as  far  as  possible,  but 
to  look  into  an  obscure  place.  The  passages  in  which  the  men  work 
are  often  very  low  and  the  light  given  by  the  Davy  lamp  very  feeble. 
Thus  the  line  of  regard  is  directed  up  with  much  force  and  all  the 
adjustments  are  made  under .  marked  disadvantages. 

The  state  of  the  air,  the  absence  of  sunlight,  and  other  unsani- 
tary conditions  of  the  mines  tend  to  reduce  the  strength  of  the  men, 
and  they  therefore  become  easy  victims  of  the  nervous  spasm  of  the 
eye  muscles. 

Dransart  says  that  he  has  seen  a  number  of  these  cases  who  have 
had  paresis  of  the  superior  recti  or  inferior  obliques. 

Men  who  work  in  the  mines,  but  who  do  not  use  the  pick,  and 
who  are  therefore  not  obliged  to  strain  the  eyes  upward  to  such  an 
extent  as  do  the  others,  are  not  peculiarly  subject  to  the  affection. 

The  affection  as  it  occurs  among  miners  has  been  dwelt  upon  at 
some  length  here  inasmuch  as  the  history  and  phenomena  of  these 
acquired  cases  appear  to  throw  much  light  upon  the  aetiology  of  the 
class  of  cases  which  occur  in  very  early  life  and  which  continue  under 
ordinary  circumstances. 

These  persons  are  not,  as  a  rule,  forced  by  their  occupations  to 
look  far  above  the  horizontal  plane;  they  direct  the  eyes  like  the 
majority  of  people,  mostly  below  the  p]ane  of  the  horizon. 

Although  nystagmus  is  probabhr  in  all  cases  acquired,  it  may  be 
convenient  to  speak  of  those  cases  which  occur  very  early  in  life  as 
idiopathic,  while  those  which  do  not  occur  until  adult  years  and  those 
which  arise  from  pathological  conditions  are  spoken  of  as  acquired. 

Investigations  in  my  own  cases  have  shown  that  there  exist  in 
the  idiopathic  cases  very  unusual  tensions  of  the  vertically  acting 
muscles  always  combined  with  high  degrees  of  declination.  Thus, 
in  the  cases  which  have  existed  from  the  early  periods  of  life  the  sub- 
jects of  the  affection  are  required  to  make  the  most  strenous  efforts 
in  the  adjustments  of  the  eyes. 

Since  it  has  been  practicable  to  examine  these  cases  by  the  aid 
of  the  tropometer  and  the  clinoscope,  it  has  been  possible  in  quite  a 


442  ANOMALIES  OF  MOTOR  MUSCLES. 

number  of  instances  to  bring  about  a  very  notable  reduction  of  the 
oscillations. 

In  the  case  of  a  lad,  for  example,  who  had  nystagmus  in  an  ex- 
treme form  the  upward  rotations  of  each  eye  exceeded  50°,  while  the 
rotation  downward  did  not  exceed  35°.  A  careful  relaxation  of  each 
of  the  superior  recti  reducing  the  upward  rotation  to  45°  and  increas- 
ing the  downward  rotation  to  40°,  the  oscillations  were  so  greatly 
reduced  that  the  parents  of  the  lad  regarded  him  as  cured,  although 
in  steady  fixation  there  could  still  be  seen  a  slight  oscillation. 

On  the  other  hand,  in  a  case  under  the  care  of  my  son,  Dr. 
Charles  W.  Stevens,  the  upward  rotation  was  less  than  25°  for  each 
eye  with  marked  declination.  A  relaxation  of  the  inferior  recti  per- 
mitting of  a  rotation  upward  of  29°,  each  eye,  relieved  the  nystagmus 
permanently  except  when  the  gaze  is  directed  considerably  above  the 
horizon.  In  both  these  instances,  with  the  modification  of  the  rota- 
tions, the  declination  was  also  modified. 

These  are  cases  which  are  fairly  representative  of  a  considerable 
number,  but  it  has  not  in  any  of  the  cases  seemed  practicable  to  carry 
the  correction  of  the  rotations  to  the  typical  extent,  and  as  the 
declinations  in  all  these  cases  have  been  too  extreme  to  yield  fully 
to  the  efforts  at  correction,  there  has,  as  yet,  resulted  in  no  instance 
an  absolute  cure  of  the  oscillations. 

I  am  confident  that  the  hope  for  relief  in  these  so-called  idio- 
pathic  cases  must  be  based  on  the  result  of  efforts  to  improve  the 
rotations  of  the  eyes  and  to  remove,  so  far  as  practicable,  the  declina- 
tion. 

In  cases  of  congenital  cataract,  of  leucoma,  and  of  pigmentary 
retinitis,  scotoma,  etc.,  there  would  appear  to  be  only  slight  hope  for 
any  permanent  relief.  Treatment  applied  directly  to  the  oscillatory 
affection  would,  of  course,  be  useless. 

In  miners'  nystagmus,  with  which  I  have  had  no  personal  experi- 
ence, the  advice  of  Dr.  Simeon  Snell  that  the  patient  should  rest,, 
or  find  some  new  form  of  occupation,  appears  to  be  the  rational 
course;  yet  in  these  cases  it  would  appear  that  an  investigation  by 
the  tropometer  and  the  clinoscope  might  lead  to  a  relief  to  the  con- 
ditions on  which  the  affection  is  based. 

In  a  case  of  Bernheimer's,1  in  which  the  patient  was  hyperme- 
tropic  and  in  which  the  oscillation  occurred  after  continued  close  eye 


1  Bericht    iiber    die    29    "Versammnlung    der    Ophthalmologischen    Gesell- 
schaft,"  1901. 


TALANTROPIA.  443 

work,  the  trouble  disappeared  when  the  patient  used  an  appropriate 
glass.  In  another  of  the  same  author's  cases,  in  which  there  was 
catarrhal  affection  of  the  conjunctiva  with  burning  of  the  lids,  it 
sufficed  to  draw  the  upper  lid  upward  or  the  lower  lid  down  to  relieve 
the  oscillation. 


PAET  IV. 

ANOMALOUS  CONDITIONS  OF  THE  MOTOK  APPARATUS 

OF  THE  EYES  NOT  CONSISTENT  WITH  THE 

PHYSIOLOGIC         STATE. 

Class  V. 

SECTION  LX. 

COLYTROPIA.— SPASM,    PARALYSIS,    OBSTRUCTION,    ETC. 

Deviations  of  the  visual  lines  not  consistent  with  the  physiological 
state  of  the  motor  muscles  and  nerves. 

The  conditions  of  this  class  are  usually  the  result  of  paralytic  or 
mechanical  causes.  Such  deviations  may  be  classified  as  colytropic 
or  paralytic  esotropia,  colytropic  or  paralytic  exotropia,  etc. 

It  has  been  the  custom  of  authors  to  include  under  the  head  of 
paralysis  the  various  forms  of  hindrance  to  the  movements  of  the 
eyes  which  may  arise  from  different  causes.  This,  while  convenient, 
cannot  be  regarded  as  always  strictly  correct.  For  example,  Mauthner 
mentions  at  considerable  length  as  one  of  the  causes  of  paralysis  of 
the  abducens  a  congenital  absence  of  that  muscle.  It  cannot  be  con- 
sidered quite  consistent  to  speak  of  a  paralysis  of  a  muscle  which 
never  had  an  existence.  The  obstructions  to  movement  also  which 
occur  from  the  presence  of  tumors  in  the  orbit  are  classified  under 
paralysis,  yet,  as  a  matter  of  fact,  the  muscles  of  the  eyes  may  be  in 
perfect  health.  It  is  not  then  too  much  to  require  in  any  system 
which  professes  to  classify  the  various  anomalies  and  affections  of 
the  ocular  muscles,  a  more  comprehensive  term  than  paralysis  to 
express  the  different  hindrances  to  motion  to  which  these  muscles 
are  subjected. 

Several  classifications  of  the  motor  disturbances  of  the  eyes  are 
extant,  all  somewhat  involved  and  all  more  or  less  defective.     I  shall 
therefore  venture  no  apology  for  the  introduction  of  a  new  one. 
(444) 


COLYTROPIA.  445 

These  motor  disturbances  may  therefore  be  classified  as  fol- 
lows :— 

COLYTROPIA. 

A  hindrance  or  obstruction  to  the  movements  of  the  eyes  (Greek, 
KtoXveu/,  to  hinder,  to  prevent). 

Divisions. 

1.  (a)   Spasm,     (b)    Word  blindness. 

2.  Paralysis. — Failure  of  the  nerve  influence  to  affect  contrac- 
tions of  muscles. 

3.  Obstruction. — A  mechanical  hindrance  to  the  movements  of 
the  eyes  through  the  influence  of  the  muscles,  not  of  necessity  involv- 
ing any  disease  or  disability  of  the  muscles  themselves. 

4.  Trauma. — Injuries  to  the  eye  muscles  by  which  their  action 
is  restricted  or  abolished. 

5.  Arrest    or   absence    of   development    or    degeneration    of   the 
muscles. 

Mauthner  divides  the  aetiological  causes  of  paralysis  of  the  eye 
muscles  (which  includes  the  various  divisions  of  this  classification) 
into  several  categories.  Thus  the  proximate  cause  he  calls  the  aetio- 
logical moment  (factor,  acting  cause)  of  the  first  category.  For 
example,  if  a  right-sided  oculo-motor  paralysis  is  conditional  upon 
compression  of  the  nerve  roots  at  the  base  of  the  cranium,  the  com- 
pression is  the  ffitiological  moment  of  the  first  category.  If  the  com- 
pression results,  for  example,  from  the  presence  of  a  tumor  which 
interferes  with  the  conductivity  of  nerve  influence,  then  the  tumor, 
which  is  the  cause  of  the  compression,  is  the  astiological  moment  of 
the  second  category. 

Finally,  following  out  the  example,  should  the  tumor  prove  to 
be  of  syphilitic  origin,  then  the  disease  which  has  given  rise  to  the 
tumor  is  the  aBtiological  moment  of  the  third  category. 

We  have  then,  in  their  order,  the  proximate  cause,  compression, 
the  intermediate  cause,  the  tumor  and  the  ultimate  cause,  the  con- 
stitutional disease,  constituting  the  etiological  moments  of  the  first, 
second,  and  third  categories. 

There  is  abundant  reason  for  such  an  arrangement,  for  should 
compression  be  assigned  as  the  cause  of  paralysis  in  one  case,  a  tumor 
in  the  second  and  a  constitutional  disease  in  a  third,  all  three  cases 


446  COLYTROPIA. 

may,  in  fact,  be  of  the  same  nature,  but  each  may  be  assigned  to  a 
different  class. 

If  \ve  have  passed  to  the  diagnosis  of  the  ultimate  cause,  that  is, 
to  the  ffitiological  moment  of  the  third  category,  the  indication  for 
rational  treatment  is  clear.  If  we  have  passed  no  further  than  the 
proximate  cause,  the  aatiological  moment  of  the  first  category,  we 
know  not  whether  the  pressure  is  caused  by  a  tumor,  an  enlarged 
artery,  or  an  abscess;  the  line  of  procedure  in  treatment  is  by  no 
means  clear. 

While  in  the  following  pages  neither  the  order  nor  the  termin- 
ology of  Mauthner  is  to  be  followed,  it  will  be  the  aim  to  lead  to  a 
clear  understanding  of  the  causes  which  may  determine  the  various 
forms  of  disability  by  tracing,  as  far  as  it  is  possible,  each  causative 
influence  from  the  proximate  to  the  intermediate,  and  finally  to  the 
ultimate  conditions  upon  which  the  hindrance  of  motion  may  depend. 

As  to  the  seat  of  the  proximate  condition  in  any  particular  form 
of  colytropia,  it  may  be  found  in  the  brain  cortex,  in  the  white  sub- 
stance, in  the  nucleus  for  the  oculo-motor  nerves,  along  the  fibers 
which  pass  between  the  nucleus  and  the  nerve  stem,  in  the  course  of 
the  nerve  at  the  base  of  the  cranium,  and  finally  within  the  orbit. 

SECTION  LXL 
SPASM.     SPASMODIC  COLYTROPIA. 

The  subdivisions  of  this  division  are: — 

1.  Tonic  spasm. 

2.  Clonic  spasm. 

3.  Incoordinate  movements. 

4.  Nystagmus    (from  cortical   disease). 

As  the  causes,  proximate,  intermediate,  or  ultimate,  of  the  first 
three  of  these  subdivisional  conditions  of  spasm  are  usually  situated 
in  the  cortex  of  the  cerebrum,  and  th*e  fourth,  in  a  limited  accepta- 
tion of  the  term  nystagmus  is  also  in  certain  cases  a  manifestation 
from  cortical  disease,  it  will  be  necessary  only  to  examine  the  rela- 
tions between  these  phenomena  and  cortical  lesions. 

The  subject  of  nystagmus,  in  the  more  general  sense  of  the  term, 
the  functional  form,  has  already  been  discussed. 

Although  cortical  lesions  as  direct  causes  of  oculo-motor  paral- 
ysis are  at  present  only  hypothetical,  the  relation  between  certain 
forms  of  spasmodic  disturbances  of  the  eye  muscles  and  cortical 


SPASM.  447 

lesions  is  in  a  definite  way  established.  There  occur  cases  in  which, 
from  pressure  or  injury  of  the  cortex,  certain  reactions  upon  the  eye 
muscles  are  observed,  yet  the  location  of  the  pressure  and  the  especial 
form  of  the  muscular  reaction  are  not  so  closely  associated,  so  far  as 
the  present  state  of  knowledge  extends,  as  to  permit  of  the  prediction 
that,  under  certain  circumstances  of  cortical  change,  certain  mus- 
cular phenomena  will,  of  necessity,  follow.  For  example,  with  sup- 
purative  meningitis,  in  which  there  is  pressure  upon  the  anterior 
and  parietal  lobes  of  the  cerebrum,  there  may  occur  a  conjugate 
deviation  of  the  eyes  or  a  spasm  of  convergence,  but  the  region  over 
which  this  pressure  must  be  made  is  not  clearly  defined,  nor  does 
the  deviation  of  the  eyes  always  occur  under  what  appear  to  be  prac- 
tically similar  circumstances. 

From  the  discoveries  of  Hitzig,  •  Ferrier,  Horsley,  Beevor,  and 
others  it  seems  reasonable  to  suppose  that  there  is  a  cortical  region 
which  in  some  way  influences  the  impulse  directed  to  the  eye  mus- 
cles; the  nuclear  region  at  the  floor  of  the  third  ventricle  and  the 
aqueduct  of  Sylvius  being  the  immediate  and  direct  station  from 
which  the  specific  influence  is  passed  to  the  nerves  supplying  the 
muscles.  The  assumed  association  is  shown  in  Bernheimer's  dia- 
gram at  page  82. 

While  it  is  known  that  disease  or  pressure  upon  definite  parts 
of  the  nuclear  region  will  invariably  induce  paralysis  of  certain  of 
the  eye  muscles,  and  the  precise  muscle  can  be  predicated  from  an 
approximate  point  of  lesion  of  the  nucleus,  at  least  so  far  as  certain 
nuclear  groups  are  concerned,  no  such  prediction  can  be  made  in 
regard  to  the  effect  of  cortical  lesions  in  inducing  spasm. 

The  number  of  different  forms  of  ocular  muscular  disturbances 
arising  from  cortical  lesions  thus  far  clearly  made  out  is  quite  small, 
and  may  be  said  to  include  only  conjugate  deviation,  spasmodic  con- 
vergence, falling  of  the  upper  lid  (ptosis),  contraction  of  the  pupil, 
and  some  clonic  convulsive  movements,  which  are  sometimes  spoken 
of  as  nystagmus.  This  term  is  hardly  appropriate  to  these  move- 
ments, which  differ  materially  from  those  of  the  ordinary  forms  of 
nystagmus.  To  this  list  of  irregular  phenomena  may  be  added  a  con- 
dition of  absence  of  ability  to  regulate  the  movements  of  the  eyes, 
although  the  power  of  movement  may  remain  intact.  Thus,  while 
each  eye  may  retain  the  power  to  rotate  inward  separately,  the  faculty 
of  combined  convergence  may  be  absent.  (Parinaud.) 

Beyond   these   occasional    and    apparently    not    always    uniform 


448  COLYTROPIA. 

phenomena,  neither  anatomical  research  nor  pathological  observations 
have  thus  far  so  definitely  located  a  given  portion  of  the  cortex  as 
the  region  from  which  spasm  of  special  ocular  muscles  must  orig- 
inate that  it  can  be  said  that  a  lesion  of  an  exact  region  will  be  fol- 
lowed by  a  definite  phenomenon  of  the  muscles. 

The  discoveries  and  discussions  bearing  upon  this  subject  are  of  much 
physiological  interest  and  cannot  be  profitably  overlooked  by  the  student  of 
the  ocular  muscles,  even  though  up  to  the  present  time  the  practical  results 
are  meager  and  unsatisfactory.  A  knowledge  of  what  has  already  been 
observed  may  fortunately  lead  to  new  observations  which  may  place  the  whole 
subject  in  better  light. 

The  once  accepted  doctrine  of  Flourens1  that  a  single  part  of  the  brain 
could  assume  the  function  of  any  or  of  all  other  parts,  was,  at  least  in  some 
measure,  overturned  by  the  discovery  of  the  localized  lesion  in  relation  to 
aphasia. 

That,  however,  nervous  influence  may  be  transmitted,  either  afferently 
or  efferently,  through  one  cortical  center  to  another  has  been  demonstrated 
in  a  number  of  instances.2 

A  revolution  in  all  the  preconceived  notions  on  the  subject  followed  the 
notable  discoveries  of  Fritsch  and  Hitzig3  and  the  epoch-making  works  of 
Ferrier,4  of  Horsley  and  Schiifer,5  Beevor,8  Golz,T  Munk,8  and  Exner."  With  the 
appearance  of  these  and  other  works  arose  a  new  physiology  of  the  nervous 
system. 

While  the  doctrine  of  cerebral  localization  has  been  generally  accepted, 
it  is  to  be  conceded  that  there  remains,  especially  in  respect  to  a  cortical  center 
controlling  the  movements  of  the  eyes,  much  to  be  discovered. 

Among  the  earliest  of  these  localizations  was  that  by  Bouillaud,10  who 
recorded  clinical  facts  which  pointed  to  a  connection  between  lesions  of  the 
anterior  portion  of  the  cerebrum  and  loss  of  speech. 

It  remained,  however,  for  Broca,  in  1801,  to  establish  the  definite  relations 
between  lesions  of  the  base  of  the  third  convolution,  more  particularly  of  the 
left  hemisphere,  and  the  condition  of  aphasia.1  Later,  Hughlings  Jackson2 


1  "Keserches  Experimentales  sur  les  Proprietes  et  les  Fonctions  du  System 
Xervrux." 

2  For  a  recent  and  very  interesting  case  see  that  of  Dr.  Harvey  Gushing, 
reported  by  Professor  Geo.  T.  Ladd  in  Popular  Science  Monthly,  Avigust,  1905. 

3  Reichert  und  DuBois-Raymond's  Archiv.,   1870.     "Untersuchungen  iiber 
das  Gihirn./'  1874. 

4 David  Ferrier:     "Cerebral  Localization." 

5  Horsley  and  Schiifer:     "Philosophical  Transactions,"  1888. 

0  Horsley  and  Beevor:     ""Philosophical  Transactions,"   1890. 

7  Frederic   Golz    (Strasburg)  :     Six   memoirs   entitled  "Verrichtungen   des 
Grosshirns,"  in  Pfluger's  Archives,  1876  to  1888. 

8  Uber  die  Functionen  der  Grosshirnrinde,"  1880. 

9  "Localization  der  Functionen  in  der  Grosshirnrinde  des  Menchen,"  1881. 

10  Archives  de  Medecine,  1825. 
"Ferrier:     "Cerebral   Localization." 

13  "Clinical  and  Pathological  Researches  on  the  Nervous  System." 


MOTOR  AREA  FOR  THE  EYES.  449 

found  that  there  was  a  relation  between  lesions  situated  in  regions  near  and 
related  to  the  corpus  striatum  and  general  or  localized  convulsions.1  To  these 
convulsions  was  given  the  name  "Jacksonian  epilepsy.'' 

It  is  extremely  unfortunate  that  the  convulsive  disease  thus  known 
should  be  included,  even  in  terms,  with  epilepsy.  The  two  conditions,  if  they 
do  not  differ  as  widely  as  blindness  and  deafness,  are  surely  no  more  the  same 
than  are  typhoid  fever  and  smallpox.  Each  of  these  later  diseases  is  charac- 
terized by  cutaneous  eruption  and  fever;  so  epilepsy  and  "Jacksonian  epi- 
lepsy" are  characterized  by  convulsions  and  generally  loss  of  consciousness, 
but  neither  the  aetiology  nor  the  nature  of  the  diseases  have  any  further  rela- 
tion. Why  should  not  the  convulsive  disease  dependent  upon  gross  manifest 
cerebral  lesions  and  having  symptoms  peculiar  to  itself  have  a  name  which 
will  not  confound  it  with  a  disease  not  dependent  upon  any  such  lesion? 

The  doctrine  of  cerebral  localizations  was,  however,  established  by  the 


Fig.  175. — Motor  Area  for  the  Eyes,  according  to  Beevor  and  Horsley. 

discovery  of  Fritsch  and  Hitzig,2  who,  in  1870,  showed  that  by  the  direct  appli- 
cation of  electrical  stimulant  to  pretty  definite  cortical  regions  certain  rather 
definite  movements  could  be  excited. 

The  subject  was  then  taken  up  by  Ferrier  and  others,  especially  by  Beevor 
and  Horsley,  who  located  the  region  of  the  movements  of  the  eyes  just  behind 
the  prefrontal  lobe  or  between  the  prefrontal  and  precentral  sulcus  in  a  space 
continued  upward  to  the  longitudinal  fissure.3  In  this  region  stimulation 
"causes  opening  of  the  eyes,  dilatation  of  the  pupils,  and  movements  of  the 
head  and  eyes  to  the  opposite  side." 

The  accompanying  diagram  (Fig.  175),  copied  from  Beevor  and  Horsley/ 
but  indicating  only  the  centers  for  the  eye  movements,  shows  the  location  of 
this  region  as  made  out  by  them. 

As  a  matter  of  fact,  others  found  that  the  region  in  which  such  move- 


1  Ferrier :     Loc.  tit. 

2  Loc.  cit. 

3 Ferrier:     "Cerebral  Localization,"   p.  27. 
*  Philosophical  Transactions,   1890. 

29 


450  COLYTROPIA. 

merits  can  be  induced  is  much  more  extensive,  including,  besides  the  frontal, 
much  of  the  parietal  lobe. 

Ferrier  suggests  that  the  movements  of  the  eyes  are  "the  signs  of  aroused 
subjective  visual  sensation  and  due  to  the  associated  action  of  the  frontal  or 
subcortical  oculomotor  centers.''1 

The  movements  of  the  eyes  cannot  be  abolished  without  the  removal  of 
the  whole  of  the  frontal  lobe. 

In  regard  to  the  intermediate  and  ultimate  causes  of  the  dis- 
turbed action  of  the  oculo-motor  muscles  from  cortical  lesions  there 
is  as  little  variety  as  in  the  phenomena  themselves. 

With  acute  inflammation  of  the  meninges,  inflammation  with 
suppuration,  the  presence  of  purulent  deposit  may  cause  pressure 
upon  the  region  of  the  cortex  influencing  the  motor  muscles  of  the 
eyes.  The  same  is  true  of  cerebro-spinal  meningitis.  With  tuber- 
cular meningitis  the  pressure  may  arise  from  tubercular  deposits. 
With  each  of  these  forms  of  meningeal  inflammation  may  occur  con- 
traction of  the  pupils,  spasm  of  convergence,  conjugate  turning  of 
the  eyes,  incoordinate  movements,  clonic  twitchings,  and  ptosis. 
Osteoplasms  and  other  tumors,  by  pressure  upon  the  cortex,  may  in- 
duce similar  results. 

All  of  these  conditions  may  at  length  give  way  to  paratysis  of 
the  eye  muscles,  when  it  is  probable  that  the  disease  has  extended  to 
the  nuclear  region. 

The  pupil  is  then  enlarged,  the  spasm  of  the  long  muscles  gives 
place  to  inability  to  contract,  and  complete  or  incomplete  ophthal- 
moplegia  is  established. 

WORD  BLINDNESS.     PSYCHIC  COLYTROPIA. 

In  this  connection  should  be  mentioned  a  most  interesting  con- 
dition resulting  from  lesion  of  the  anterior  lobe  which  takes  the 
form  of  "word  blindness/' 

In  this  singular  trouble,  first  described  by  Kussmaul,  there  is  the 
ability  to  write,  but  not  to  read.  In  some  cases  the  inability  to  read 
extends  ^>nly  to  words,  while  in  other  cases  the  ability  to  distinguish 
individual  letters  is  wanting.  The  ability  to  see  the  letters  is  not 
wanting,  but  the  interpretation  of  the  sign  is  absent. 

This  curious  affection  has  not,  up  to  this,  been  regarded  as  hav- 
ing any  relation  to  the  muscles  of  the  eyes,  yet  it  appears  to  me  that 
it  should  be  classed  among  the  affections  of  the  eye  muscles. 


1  Ferrier :    LOG.  cit.,  p.  39. 


WORD  BLINDNESS.  451 

If  we  refer  to  the  discussion  of  the  physiology  of  the  visual  sense 
of  space  dimensions  (p.  1.24  to  137),  it  will  be  seen  that  the  concep- 
tion of  the  form  of  objects  is  not  derived  directly  from  the  traditional 
retinal  picture,  but  from  the  sense  of  movements  made  by  the  eyes. 
But  that  these  movements  of  the  eyes  are  coordinated  and  interpreted 
within  the  cortical  portion  of  the  brain  is  most  probable,  a  view 
corresponding  to  that  of  Ferrier  above  quoted.  If  by  a  lesion  of  a 
certain  portion  of  the  cortex  it  becomes  impossible  to  interpret  these 
small  muscular  movements  required  in  obtaining  the  concept  of  the 
word,  then  the  signs  can  have  no  meaning.  In  the  absence  of  the 
power  to  coordinate  these  movements  of  the  eyes,  there  may  remain 
a  power  to  coordinate  the  movements  of  the  arm  and  hand,  and  hence 
the  act  of  writing  may  be  accomplished  with  little  if  any  difficulty. 

Some  of  these  patients,  indeed,  who  can  recognize  individual 
letters  but  do  not  recognize  words,  resort  to  the  device  of  writing  the 
word,  the  motion  of  the  hand  serving  to  interpret  the  combination  of 
letter  signs. 

As  to  the  locality  of  the  lesion,  Charcot  found  it  situated  in 
the  inferior  parietal  lobe,  and  Dejernine  and  Serieux  have  more 
exactly  placed  it  at  the  fold  at  the  posterior  part  of  the  inferior  lobe. 

Word  blindness,  then,  may  be  regarded  as  the  effect  of  a  loss  of 
power  to  coordinate  and  to  interpret  the  movements  made  by  the 
eye  muscles  when  these  movements  are  slight,  as  in  the  act  of  seeing 
letters,  and  when  the  objects  seen  are  conventional  signs. 

In  the  larger  movements,  such  as  are  required  of  the  eyes  in 
walking  or  in  separating  and  counting  the  spots  on  the  blocks  in  the 
game  of  dominos,  the  coordinating  faculty  is  sufficient,  but  in  the 
case  of  the  succession  of  letters  of  a  word  it  is  insufficient  for  the  pur- 
pose of  interpretation  and  possibly  for  the  purpose  of  determining 
upon  the  movements  to  be  executed  through  the  influence  of  the 
nuclear  centers. 

This  view  is  in  harmony  with  the  hypothesis  of  Xothnagel,1  that 
the  parietal  lobe  is  the  seat  of  the  centers  for  the  muscular  sense. 

This  muscular  sense,  which  is  too  much  overlooked,  is  in  fact  the 
sense  on  which  the  act  of  reading  is  based.  The  mere  visual  impres- 
sion of  letters  upon  a  retina  the  movements  of  which  could  not  be 
felt  at  the  center  for  such  movement  sense  would  fail  to  convey  the 
idea  of  Avords  and  sentences. 


'Neurolog.  Centralblatt,  p.  213,  1887. 


4,52  COLYTROPIA. 

Terrier  quotes  Charcot  as  writing:  "Cases  may  be  seen  in  which 
the  sense  position  of  the  limbs  was  entirely  abolished,  and  yet  the 
patients  were  able  to  move  the  affected  members  freely  even  when 
the  eyes  were  closed." 

Hence,  with  a  failure  to  direct  or  to  experience  the  sense  of 
movements,  there  may  be  an  ability  to  move  the  eyes,  and  they  may 
move  in  a  spasmodic,  irregular,  and  incoordinate  manner.  This  is 
what  happens  in  certain  cases  of  meningitis,  of  abscess  of  the  brain  at 
the  anterior  and  parietal  region,  and  of  bony  hypertrophy  of  the 
skull  at  the  location  of  the  cortex  assigned  as  that  for  the  movements 
of  the  eyes. 

Mention  is  made  in  text-books  of  ophthalmology  of  other  spasms 
of  the  eyes  not  associated  with  cerebral  disease.  Most,  if  not  all  the 
conditions  described  are  somewhat  unusual  forms  of  heterophoric 
anomalies.  A  condition  of  pronounced  hyperphoria,  for  example, 
which  had  escaped  observation  suddenly  becomes  so  manifest  as  to 
become  troublesome.  The  case  is  set  down  to  the  account  of  spasm 
without  further  investigation.  In  a  general  way  facts  of  this  order 
may  be  said  to  cover  the  cases  of  hysterical  and  other  supposed  spasms 
which  occupy  some  space  in  the  literature. 

When  definite  and  exact  observations  of  the  eye  movements  are 
made  such  spasms  are  rarely  if  ever  found. 


SECTIOX  LXTT. 
PARALYSIS.     PARALYTIC  COLYTROPIA. 

(a)  SINGLE,     (b)  MULTIPLE. 

According  to  the  location  of  the  proximate  cause  paralysis  may 
be  subdivided  into  : — 

Central   (intercranial,  Mauthner). 

Intermediate. 

Peripheral. 

Central  paralysis  may  be  again  subdivided  into  nuclear  and 
fascicular. 

Intermediate  paralysis  has  no  subdivisions. 

Peripheral  paralysis  is  subdivided  according  to  the  individual 
muscles  affected ;  e.g.,  failure  of  action  of  the  abducens  nerve  in- 
duces paralysis  of  the  external  rectus,  etc. 

Paralytic  affections  of  the  motor  eye  muscles  arising  from  vari- 


PARALYSIS.  453 

ous  causes  and  from  causes  situated  in  the  various  locations  above 
mentioned  have  certain  manifestations  in  common  by  means  of  which 
a  diagnosis  of  the  affected  muscle  or  muscles  may  be  arrived  at. 

Before  entering,  therefore,  upon  a  discussion  of  the  special 
classes  of  the  affection  as  they  depend  upon  the  location  of  the  cause 
of  the  disturbance,  it  will  be  convenient  to  examine  the  symptoms  of 
paralysis  common  to  all  the  classes.,  and  present  in  greater  or  less 
degree  in  all  cases. 

Certain  of  these  symptoms  are  more  pronounced,  or  at  least 
more  conspicuously  present  to  the  attention  of  the  individual  affected, 
in  recent  than  in  old  cases.  This  is  especially  true  of  visual  confusion, 
of  vertigo,  and  of  a  false  sense  of  orientation;  for  while  all  these 
conditions  persist,  custom,  after  a  greater  or  less  period  of  time, 
modifies  the  intensity  of  these  symptoms  even  to  the  extent  that  in 
some  instances  they  may  not  be  observed  by  the  patient  except  as 
attention  is  especially  directed  to  them. 

Diplopia  also,  which  is,  in  pronounced  cases  of  recent  paralysis, 
often  a  most  annoying  symptom,  largely  disappears  in  advanced  cases 
of  nuclear  paralysis. 

Among  the  earliest  and  the  most  persistent  of  the  subjective 
symptoms  of  eye  muscle  paralysis  is  the  erroneous  localization  of 
objects  in  the  visual  field.  This  false  localization  is  for  the  most 
part  in  the  direction  of  the  action  of  the  affected  muscle.  If,  for 
example,  the  person  with  paralysis  of  the  external  rectus  of  the  right 
eye  attempts  quickly  to  seize  with  the  hand  an  object  at  his  right 
side,  he  is  liable  to  miss  it  by  extending  the  hand  beyond  the  object. 
If  he  points  quickly  with  the  finger  to  an  object  on  that  side  he  also 
points  beyond  to  the  right  of  the  object.  If  he  takes  a  longer  time 
he  may  correct  the  error  by  the  help  of  the  other  eye,  but,  except  by 
the  aid  of  the  well  eye  or  by  the  correcting  sense  of  touch,  the  object 
at  the  right  will  persist  in  appearing  in  a  false  position. 

The  reason  for  this  false  projection  is  evident.  Experience  with 
the  unaffected  eye  or  with  both  eyes  during  the  years  of  freedom  from 
the  affection,  as  well  as  native  consciousness,  have  taught  the  patient 
the  relation  between  the  nervous  impulse  and  the  effect  upon  the 
direction  of  the  eye.  But  if  now  a  greater  impulse  is  demanded  to 
place  the  eye  in  the  given  position,  or  if  the  impulse  fails,  the  posi- 
tion of  the  object  is  estimated  by  the  force  of  the  nervous  impulse 
directed  to  the  effort  to  move  the  eye.  Hence,  the  greater  the  dis- 


454  COLYTROPIA. 

ability  of  the  muscle,  the  greater  the  apparent  displacement  of  the 
object  toward  the  side  of  the  affected  muscle. 

This  erroneous  localization  of  objects  in  the  field  of  vision  often 
becomes  a  matter  of  serious  consequence  to  the  patient  in  walking. 
He  is  liable  to  collide  with  the  furniture  of  a  room  or  objects  in  the 
street. 

A  patient  complained  that,  as  he  was  obliged  to  go  to  his  busi- 
ness early  in  the  morning,  before  the  barrels  of  ashes  were  removed 
from  the  sidewalk,  he  almost  invariably  ran  against  the  ash  barrels 
although  he  was  constantly  on  his  guard  to  avoid  them. 

In  cases  in  which  the  vertically  acting  muscles  are  affected,  the 
act  of  going  up  and  down  stairs  becomes  perplexing. 

This  false  orientation  induces  another  manifestation  of  paralytic 
disturbance,  the  visual  -vertigo,  which  is  often  a  most  troublesome 
symptom.  This  symptom  is  intensified  when  the  patient  attempts 
visual  acts  which  demand  quick  and  especially  complicated  move- 
ments of  the  eyes,  the  visual  aid,  for  example,  which  is  required  in 
going  up  and  down  stairs,  especially  the  latter,  the  watching  of  the 
landscape  from  a  window  of  a  moving  railroad  train,  etc.  The  vertigo 
often  induces  nausea  and  all  the  symptoms  of  seasickness.  That  the 
symptom  depends  entirely  upon  the  false  orientation  is  easily  shown, 
since,  if  the  paralyzed  eye  is  covered,  the  confusion,  vertigo,  and 
nausea  disappear. 

A  characteristic  adjustment  of  the  head  in  relation  to  the  body 
is  often  a  conspicuous  symptom  of  paralysis  of  an  eye  muscle.  This 
is  especially  true  of  paralysis  of  the  superior  recti  muscles.  In  this 
case  the  chin  is  raised  and  the  forehead  thrown  back.  In  paralysis 
of  an  externus  the  head  turns  toward  the  side  of  the  unaffected  mus- 
cle. The  pose  of  the  head  in  anomalous  states  of  the  muscles  has 
already  been  discussed  in  the  chapter  on  the  expressions  of  the  face, 
and  the  principles  there  laid  down  apply  in  conditions  of  paralysis 
but  the  manifestations  are  usually  greatly  intensified. 

The  subjective  phenomenon  most  noticeable  to  the  patient  and 
most  valuable  to  the  physician  in  the  direction  of  diagnosis  is  the 
diplopia  which  is  present  in  fresh  cases,  and  usually  in  old  cases,  in 
some  part  of  the  field  of  regard. 

A  careful  examination  of  the  phenomena  of  diplopia  will  gen- 
erally determine  the  muscle  or  muscles  whose  actions  are  limited,  but 
further  considerations  are  necessary  in  locating  the  seat  of  the  lim- 
itincr  cause. 


PARALYSIS  OF  EXTERNAL  RECTUS.  455 

111  order  then  to  interpret  the  meaning  of  the  double  images  it 
will  be  necessary  to  study  first,  the  effects  of  restrictions  of  movements 
of  individual  muscles. 

The  peculiarities  of  diplopia  will  vary  according  to  the  muscle 
or  the  pair  affected. 

PARALYSIS  OF  THE  EXTERNAL  RECTUS. 

The  diplopia  will  occur  when  the  gaze  is  turned  in  the  direction 
of  the  action  of  the  paralyzed  muscle.  For  example,  if  the  affected 
muscle  is  the  external  rectus  of  the  right  eye,  the  diplopia  will  mani- 
fest itself  as  the  gaze  is  directed  toward  the  right. 

The  double  images  will,  if  the  head  is  in  the  primary  position 
and  the  gaze  is  in  the  plane  of  the  horizon,  be  exactly  level,  and  the 
image  of  the  right  eye  will  appear  further  to  the  right  than  that  of 
the  left,  that  is,  the  diplopia  will  be  one  in  which  the  image  is  on 
the  side  of  the  eye  which  sees  it,  and  it  will  be  homonymous  diplopia. 
Moreover,  if  the  affection  is  confined  to  the  muscle  named  and  there 
is  no  marked  anomaly  in  the  normal  position  of  the  retinal  meridians, 
each  image  will  be  exactly  erect. 

In  the  case  of  paralysis  of  the  external  rectus  of  the  right  eye  the 
left  eye  is  so  directed,  when  looking  at  an  object  at  the  right,  that  the 
image  falls  at  the  macula.  Therefore,  this  eye  projects  the  image  in 
the  direction  of  the  object;  but  since  there  is  a  limitation  of  move- 
ment of  the  right  eye  toward  the  right  side,  this  eye  lags  behind  and 
the  image  of  the  object  is  impressed  at  the  left  of  the  macula,  and 
by  the  rule  (Section  XXXIV)  the  image  is  displaced  to  the  right 
in  proportion  to  the  extent  of  the  displacement  of  the  impression 
toward  the  nasal  side  of  the  retina.  If  the  object  is  moved  further 
and  further  to  the  right  while  the  head  remains  in  the  primary  posi- 
tion, the  images  will  separate  more  and  more,  the  image  of  the  right 
eye  being  thrown  further  and  further  to  the  right  of  that  of  the  left 
eye.  So,  also,  the  distance  between  the  images  will  be  augmented  in 
proportion  to  the  degree  of  paralysis. 

In  a  small  class  of  cases  in  which  there  is  a  marked  limitation  of 
movement  in  the  direction  of  the  external  rectus  muscle,  there  is 
neither  vertigo,  nausea,  false  projection,  secondary  deviation,  nor,  in 
the  median  field  of  regard,  converging  strabismus.  There  may,  in- 
deed, be  slight  exophoria  or  even  exotropia. 

Such  a  case  is  represented  in  Figs.  17G  and  177.     This  is  a  case 


456 


COLYTROPIA. 


of  limitation  of  rotation  of  the  left  eye  outward,  such  as  is  classed 
with  paralysis  of  the  abducens.  It  is  easy  to  see  in  the  first  of  these 
two  figures  that  there  is  no  converging  strabismus,  and  it  is  equally 
plain,  in  examining  the  second  figure,  that  when  the  attempt  is  made 
to  carry  the  regard  to  the  left  the  right  eye  turns  freely  in  that  direc- 
tion while  the  left  remains  stationary.  Had  another  picture  been 
taken  to  show  the  position  of  the  eyes  when  the  regard  was  carried 


Fig.  176.  Fig.  177. 

Paralysis  of  External  Rectus,  Left  Eye.  In  Fig.  176  the  child  looks 
straight  forward  without  squinting.  In  Fig.  177  the  gaze  is  turned  toward 
the  left,  but  the  left  eye  does  not  move  outward. 

to  the  right  it  would  be  seen  that  both  eyes  followed  in  the  usual 
harmonious  relation. 

The  affection  dates  from  early  childhood  and  the  mother  thinks  that  it 
was  not  observed  until  after  an  attack  of  whooping-cough  at  the  age  of  2  years 
and  more.  I  suspect  that  it  really  dates  earlier. 

The  rotations  as  shown  by  the  tropometer  are  as  follows:  — 

11.  E.,  up,  30°  ;    down,  60°  ;    in,  50°  ;    out,  60°. 

L.  E.  up,  30° ;    down,  60° ;    in,  40°  ;    out,  10°. 

The  rotation  out  of  10°  is  common  in  nearly  all  cases  of  paralysis  of  the 
abducens  and  is  probably,  in  general,  induced,  as  it  is  said  by  Mauthner,  by  the 
action  of  the  obliques. 

The  patient,  an  extremely  bright  girl  of  11,  had,  in  looking  straight 
through  the  phorometer,  exophoria  3°,  and  by  abduction  she  could  overcome 
10°  of  prism.  The  deviation  in  exclusion  was  for  exophoria  and  right  hyper- 
phoria  (of  which  the  phorometer  showed  1°).  There  was  no  secondary  devia- 


PARALYSIS  OF  INTERNAL  RECTUS.  457 

tion  with  gaze  in  the  primary  position.  Looking  about  10°  to  the  rigJit  there 
was  crossed  diplopia,  and  homonymous  diplopia  only  manifested  itself  in  look- 
ing about  10°  to  the  left.  Looking  up  or  down  and  straight  forward  images 
remained  united. 

Her  mother  lias  diverging  strabismus. 

The  insertion  of  the  muscle  appears  to  be  as  sharply  marked  as  its  fel- 
low, and  where  the  body  of  the  muscle  can  be  detected  it  appears  fully  devel- 
oped. 

Since  the  muscle  is  apparently  present  it  cannot  be  classed  with  cases  of 
congenital  absence  of  the  muscle,  yet  it  may  perhaps  belong  to  the  class  which 
has  been  described  by  Uhtoff,1  Baumgarten,2  and  others,  in  which  the  muscular 
tissue  is  replaced  by  connective  tissue,  with  the  form  and  insertion  of  the 
muscle,  but  without  its  functions.  It  is  also  possible  that  such  a  case  may 
belong  to  the  class  mentioned  by  Panas,3  in  which  there  may  have  occurred  a 
basal  injury  followed  by  basilar  haemorrhage. 

PARALYSIS  OF  THE  INTERNAL  EECTUS. 

In  the  case  of  paralysis  of  this  muscle  there  is  a  restriction  of 
the  rotation  of  the  eye  in  the  direction  of  the  action  of  the  muscle. 
The  eye  may  rotate  toward  the  temple  freely,  but  toward  the  median 
plane  its  action  is  limited.  In  pronounced  paralysis  there  is  diverg- 
ing strabismus.  In  this  case  the  relative  position  of  the  double 
images  is  exactly  the  reverse  of  that  in  the  case  of  paralysis  of  the 
externus.  The  diplopia  is  heteronymous,  the  distance  between  the 
crossed  images  increasing  as  the  object  seen  is  removed  further  to 
the  side  of  the  paralyzed  muscle. 

The  phenomenon  of  diplopia  is  explained  as  before,  but  with  the 
difference  that  the  image  of  the  object  now  travels  to  the  outer  half 
of  the  retina  as  the  object  is  moved  in  the  direction  of  the  action  of 
the  affected  muscle,  and,  as  the  image  now  appears  further  and  fur- 
ther .toward  the  affected  side,  it  becomes  more  and  more  crossed.  As 
in  the  case  of  paralysis  of  the  external  rectus  the  images  are,  under 
the  same  conditions,  in  the  same  horizontal  plane  and  each  image  is 
upright.  The  diplopia  may  be  only  observed  as  the  gaze  is  turned 
toward  the  unaffected  side,  and  if  the  paralysis  is  only  partial  it  may 
not  appear  until  the  direction  of  the  eyes  is  near  the  limitation  of  the 
field  of  regard. 

PARALYSIS  OF  THE  SUPERIOR  RECTUS. 
The  indications  of  paralysis  as  manifested  by  diplopia  in  the 


'TJhtoff:      Jahrbuch  fiir  Ophthal.,  1882. 

2  Monatische.  fiir  Augenheilk.,  iii 

8  "Transactions  International  Ophthalmological  Congress,  1884." 


458 


COLYTKOPIA. 


muscles  which  rotate  the  eyes  directly  in  and  out  have  been  found 
to  be  extremely  clear  and  devoid  of  any  complicating  phenomena. 
With  the  muscles  which  elevate  and  depress  the  gaze  new  and  com- 
plicating elements  appear. 

The  action  of  the  superior  rectus  muscle  in  health  is  not  a  direct 
rotation  of  the  cornea  vertically,  nor  is  it  even  a  rotation  upward  and 
inward  only.  It  is  a  rotation  upward,  inward,  and  around  an  axis 
represented  by  the  optic  axis. 

Again,  elevator  and  depressor  muscles  have  a  different  action 
according  to  whether  the  position  of  the  line  of  regard  is  directly  in 
front  or  toward  one  or  the  other  side.  If  the  eye  is  directed  straight 


Fie.  178. 


Fig.  179. 
In  Fie.   178,  looking 


Paralysis  of  Superior  Rectus  of  Right  Eye. 

forward;   in  Fig.  179,  looking  up. 


forward,  the  effect  of  a  paralysis  of  the  superior  rectus  is  much  more 
pronounced  than  when  the  eye  is  rotated  toward  the  nose.  On  the 
other  hand,  the  effect  is  augmented  as  the  eye  turns  outward. 

The  diplopia  of  paralysis  of  one  superior  reclus  is  mainly  ver- 
tical. It  may  not  be  present  when  the  patient  is  walking  and  looking 
toward  the  ground,  but  becomes  apparent  when  the  gaze  is  directed 
towrard  the  horizon  or  upward. 

As  the  eye  is  turned  toward  the  nose  the  superior  rectus  becomes 
less  and  less  an  elevator  muscle  and  more  and  more  a  rotator  about 
the  optic  axis.  Hence  while  the  images  will  be  separated  by  less 


PARALYSIS  OF  SUPERIOR  RECTUS.  459 

distance  when  the  eye  is  rotated  toward  the  nose,  the  difference  in 
the  positions  of  the  images  in  respect  to  their  verticality  will  con- 
stantly increase  as  the  eye  is  more  and  more  in  adduction.  If  the 
eye  is  turned  outward,  the  separation  of  the  images  becomes  steadily 
greater  in  proportion  to  the  abduction,  but  at  length,  when  the  ab- 
duction has  been  carried  beyond  the  point  where  the  muscle  draws 
exactly  upward  and  no  longer  inward,  the  elevating  action  is  reduced 
as  the  abduction  becomes  greater.  The  rotation  around  the  optic 
axis  is  less  up  to  a  certain  point,  when  it  is  absent,  and  then  begins 
in  the  opposite  direction.  These  phenomena  are  described  as  they 
occur  in  cases  in  which  the  adjustments  in  health  are  reasonably  free 
from  anomalies.  It  happens,  not  un frequently,  that  anomalies  of 
declinations  may  so  affect  the  position  and  verticality  of  the  images 
that  this  ideal  scheme  is  no  longer  applicable. 

The  diplopia  resulting  from  a  paralysis  of  a  single  superior 
rectus  will  be  manifested  in  the  vertical  direction  with  the  image  of 
the  affected  eye  higher  than  that  of  the  sound  one  when  the  object 
seen  is  near  the  horizon  or  above  it  and  when  the  gaze  is  directed 
straight  forward.  In  this  position,  when  the  gaze  is  somewhat  ele- 
vated, the  image  of  the  affected  eye  is  also  slightly  in  the  direction 
of  the  opposite  eye,  that  is,  the  diplopia  is  vertical  and  slightly 
heteronymous.  Also,  in  an  ideal  state  of  adjustments,  or  a  state 
approximating  this,  the  image  of  the  affected  eye,  the  upper  image, 
should  tilt  somewhat  toward  the  temple.  That  this  crossing  position 
of  the  images  and  this  leaning  of  the  upper  part  of  the  upper  image 
toward  the  temple  does  not  always  occur  has  been  forcibly  held  by 
Mauthner,  who  has,  at  much  length,  reiterated  the  proposition  that 
''the  obliquity  of  the  double  images  proclaimed  from  theory  has  in 
practice  no  diagnostic  value."1  A  similar  view  is  taken  by  him  in 
respect  to  the  lateral  position  of  the  upper  image. 

Other  authors2  question  this  position  and  hold  that  the  swing 
of  the  upper  image  toward  the  opposite  side  and  the  tilting  of.  the 
upper  end  toward  the  temple  constitute  essential  elements  in  the 
diagnosis  of  paralysis  of  the  superior  rectus. 

We  shall  return  to  this  question  when  the  diagnosis  of  paralysis 
of  the  rectus  superior  and  rectus  inferior,  on  the  one  hand,  and  the 
oblique  muscles  on  the  other,  is  under  consideration. 


'Mauthner:      "Aujrcnheilkunde,"  p.  530. 

2Panas:       "Maladies   des  Yeux,"   ii,   p.   44.       Fuchs:       Duane's   Transla- 
tion, p.  596. 


460  COLYTROPIA. 

PARALYSIS  OF  THE  INFERIOR  RECTUS. 

Much  that  has  already  been  said  in  reference  to  the  diplopia 
arising  from  paralysis  of  the  superior  rectus  applies  to  that  of  the 
inferior  rectus.  The  depressing  power  of  this  muscle,  like  the  lifting 
power  of  the  superior,  diminishes  as  the  eye  is  brought  into  the  posi- 
tion of  adduction,  and  its  depressing  influence  increases  in  abduction 
until  the  eye  has  rotated  outward  about  30°  from  the  sagittal  plane 
of  the  head,  when  it  again  diminishes.  Like  the  superior  rectus,  it 
aids,  in  the  condition  of  health,  in  adduction,  and  hence,  in  paralysis, 
the  eye  is  somewhat  abducted  and  the  images  cross.  So  also  the  in- 
ferior rectus  acts  as  a  rotator  of  the  eye  upon  the  optic  axis  and  in 
paralysis,  the  theoretical  states  of  the  muscles  being  in  other  respects 
correct,  the  image  of  the  affected  eye  should  lean  with  its  upper  part 
toward  the  nose. 

The  diplopia,  then,  of  paralysis  of  the  inferior  rectus  may  be 
theoretically  described  as  vertical,  the  images  of  the  affected  eye 
being  below,  crossed,  and  with  the  image  leaning  to  the  center.  The 
first  of  these  conditions  is  always  present;  the  second  and  third  may 
be  present.  But  the  important  factor  in  the  diplopia  from  paralysis 
of  this  muscle,  as  in  the  case  of  the  superior  rectus,  is,  as  Mauthner 
has  shown,  the  fact  that  as  the  eye  is  rotated  toward  the  nose  the 
separation  of  the  images  becomes  less  extensive,  while  as  the  eye  is 
rolled  toward  the  temple  the  distance  between  the  images  increases. 

PARALYSIS  OF  THE  SUPERIOR  OBLIQUE. 

While  the  oblique  muscles  act  both  in  the  vertical  and  horizontal 
directions,  their  chief  office  is  to  rotate  the  eye  on  its  own  axis.  The 
phenomena  of  diplopia  resemble  in  such  measure  those  found  in 
paralysis  of  the  superior  and  inferior  recti  that  the  diagnosis  demands 
close  observation  and  in  some  instances  the  differentiation  is  some- 
what difficult.  The  action  of  the  superior  oblique  causes  the  eye  to 
rotate  downward,  outward,  and  around  the  optic  axis.  Its  vertical 
and  lateral  action  is  diminished  as  the  eye  turns  outward,  while  the 
inclination  of  the  meridian  in  this  position  increases.  The  depressing 
action  of  the  superior  oblique  is  greater  when  the  eye  is  directed 
straight  forward  than  when  directed  toward  the  temple.  It  is  still 
greater  when  the  eye  is  rotated  toward  the  nose. 

From  these  considerations  it  will  be  seen  that  with  paralysis  of 


PARALYSIS  OF  SUPERIOR  OBLIQUE.  461 

the  superior  oblique  the  image  of  the  affected  eye  will  be  below  the 
other,  since  the  eye  will  be  deprived  of  the  action  of  one  of  the  de- 
pressor muscles,  and  that  the  diplopia  will  occur  in  the  lower  part 
of  the  field  of  regard.  Xot  only  will  the  images  be  vertically  sepa- 
rated when  looking  straight  down,  but,  since  the  diverging  action  of 
this  muscle  is  removed,  the  images  will  be  more  or  less  homonymous. 
According  to  the  theory  of  the  action  of  all  the  muscles,  the  image 
of  the  affected  eye  should  also  be  much  tilted,  with  its  upper  end 
pointing  inward.  This  apparent  tilting  inward  of  the  image  repre- 
sents in  fact  an  actual  tilting  outward  of  the  vertical  meridian  of 
the  affected  eye,  and  this  important  fact  should  not  be  lost  sight  of 
in  the  examination  of  cases;  for,  if  the  leaning  inward  of  the  image 
should  be  interpreted  as  the  rolling  inward  of  the  meridian,  it  might 
lead  to  a  false  diagnosis. 

Paralysis  of  the  superior  oblique  is,  like  that  of  the  abducens, 
of  comparatively  frequent  occurrence.  The  great  majority  of  cases 
of  paralysis  of  the  eye  muscles  is  associated  with  these  two  muscles. 

It  will  be  well  in  this  place  to  give  in  detail  the  indications  to 
be  observed  in  a  case  of  paralysis  of  the  left  superior  oblique. 

The  patient  complains  of  diplopia  when  looking  down  and  to  the 
right.  It  will  be  found  that  the  image  of  the  right  eye  is  highest  and 
there  may  be  a  slight  esophoria  (1°  or  2°),  or  there  may  be  no  devia- 
tion in  this  direction.  As  the  line  of  regard  is  turned  to  the  right 
and  down  the  images  become  more  and  more  separated.  The  image 
of  the  affected  eye  is  nearer  than  the  other.  The  images  may  both  tilt 
or  neither  may  tilt;  generally  the  latter  is  the  case.  (According  to 
the  theory  of  the  action  of  the  muscles,  there  should  be  marked  tilting 
of  the  left  eye  toward  the  right.)  If  the  line  of  regard  is  carried 
upward  the  diplopia  disappears. 

In  the  table  on  page  462  are  given  the  average  results  of  exam- 
inations in  several  cases  of  superior  oblique  paralysis  made  by  the 
aid  of  the  tropometer  and  the  clinoscope. 

It  will  thus  be  seen  that  while  the  leaning  may  not  be  observed 
in  the  ordinary  examination,  the  clinoscope  shows  about  7°  positive 
leaning  in  the  primary  position — a  leaning  not  altogether  unusual 
in  sound  eyes. 

It  becomes,  in  view  of  this,  a  question  whether,  in  case  of  such 
considerable  normal  declination,  the  habitual  state  of  tension  of  the 
superior  oblique  may  not  be  regarded  as  an  important  predisposing 


462 


COLYTROPIA. 


clement  to  the  affection  when  it  is  not  the  result  of  nuclear  disease 
dependent  upon  syphilitic  taint. 

When  a  patient  presents  himself  with  the  symptoms  of  paralysis 
of  an  eye  muscle  and  it  is  found  that  there  is  a  vertical  diplopia, 
the  question  of  diagnosis  between  the  two  pairs  of  elevator  and  de- 
pressor muscles  of  the  eyes  at  once  suggests  itself.  There  is  vertical 
diplopia.  It  can  he  induced  by  a  vertically  acting  rectus  or  by  an 
oblique  muscle. 

Table  of  Rotation*  and  Le/tnint/s  in  Superior  Oblique  Paralysis. 


Averagi;  Itesult? 

Sound  Eye 

Affected  Eye 

ROTATIONS 

Up 

40° 

40° 

Down 

40° 

40° 

In 

48° 

52° 

Out 

40° 

30° 

LEANING  OF  IMAGES 

Primary  Position 

0° 

+  7° 

Down  30° 

0° 

+  15° 

Up  20° 

0° 

+  5° 

If  we  select  the  inferior  rectus  and  the  superior  oblique  as  those 
between  the  diplopia  of  which  we  would  differentiate  we  find  the  fol- 
lowing points : — 

1.  There  is  diplopia  in  the  lower  field  of  regard  in  each  case, 
and  in  each,  as  the  gaze  is  carried  directly  down,  the  distance  between 
the  images  is  augmented.    There  is  here  therefore  a  common  character 
to  the  diplopia. 

2.  In  paralysis  of  the  inferior  rectus  the  eye  is  supposed  to  turn 
slightly  out  on  account  of  the  disability  of  a  muscle  which  normally 
acts  as  a  convergent  muscle,  while,  on  the  other  hand,  with  paralysis 
of  the  superior  oblique  there  is  supposed  to  be  a  slight  converging 
of  the  eyes  due  to  the  suppression  of  influence  of  a  diverging  muscle. 

If  these  conditions  were  uniform,  they  would  furnish  a  reliable 
and  constant  element  of  diagnosis ;  for,  should  we  find  paralysis  with 


PARALYSIS  OF  SUPERIOR   OBLIQUE.  463 

vertical  diplopia  in  the  lower  field  only,  and  with  the  image  of  the 
right  eye  at  the  right  of  the  other,  homonymous  images,  we  might 
at  once  conclude  that  the  superior  oblique  is  the  muscle  affected,  and 
should  the  images  be  crossed,  we  might  with  equal  certainty  conclude 
that  the  inferior  rectus  is  the  diasbled  muscle. 

Unfortunately  for  the  simplicity  of  diagnosis  these  conditions 
are  not  always  uniform,  and  the  fact  is  that  homonymous  diplopia  is 
sometimes  found  with  paralysis  of  the  inferior  rectus  and  crossed 
diplopia  with  paralysis  of  the  superior  oblique. 

3.  We  have  the  third  element  in  the  tilting  of  the  image  of  the 
affected  eye. 

Should  the  upper  part  of  the  image  tilt  toward  the  temple  we 
should  theoretically  locate  the  disability  with  the  inferior  rectus, 
while,  should  the  image  tilt  inward,  the  trouble  would  be  with  the 
superior  oblique. 

Here,  again,  the  failure  of  uniformity  may  militate  against  the 
correctness  of  the  diagnosis. 

Mauthner  believes  that  anomalous  conditions  like  a  normal 
divergence  or  convergence  of  the  eyes,  conditions  which  may  not  have 
been  recognized  previously  to  the  paralysis,  so  frequently  complicate 
the  diagnosis  as  to  render  the  conditions  of  No.  2  and  No.  3  without 
diagnostic  value. 

To  a  certain  extent  the  distinguished  author  is  correct  in  this, 
but  we  may  go  farther  than  this  and  we  are  more  likely  to  find  the 
true  explanation  of  the  variability  of  these  conditions. 

In  anomalous  leanings  we  find  not  only  a  satisfactory  ex- 
planation of  the  want  of  conformity  in  respect  to  the  homonymous  or 
crossed  position  of  the  images,  but  also  an  equally  clear  reason  for 
the  uncertainty  respecting  the  directions  of  tilting. 

The  anomalous  directions  of  the  vertical  meridians  which,  pre- 
vious to  the  introduction  of  the  clinoscope,  were  not  considered,  are 
now  known  to  be  common  and  of  great  practical  consequence.  We 
now  know  that  in  exceptional  instances  a  person  who  may  have  had 
fairly  comfortable  eyes  may  show  a  declination  of  from  5°  to  9°,  or 
even  more.  Such  a  declination  in  case  of  paralysis  of  a  depressor  or 
of  an  elevating  muscle  would  unquestionably  dominate,  not  only  the 
inclination  of  the  image,  but  the  divergence  or  convergence  as  well. 

Suppose  a  case  of  paralysis  of  the  left  inferior  rectus  with  a 
normal  -(-  declination  of  the  right  eye  of  7°. 

In  case  of  diplopia  an  effort  would  be  made  to  see  the  vertical 


464  COLYTROPIA. 

image  in  its  vertical  position  by  the  right  eye,  which  would  bring 
the  superior  oblique  muscle  of  that  eye  into  active  contraction.  This 
would  act  upon  the  position  of  the  vertical  meridian,  but  it  would 
give  to  the  eye  also  a  tendency  to  swing  outward.  To  counteract  this 
the  internal  rectus  would  act  and  in  many  cases,  if  not  in  most,  this 
action  of  the  right  internus  would  be  associated  with  a  synergic  action 
of  the  internus  of  the  left  eye;  hence,  a  convergence  would  be  in- 
duced. A  synergic  action  of  the  inferior  oblique  muscle  of  the  left 
eye  would  perhaps  result,  which  would  more  than  counterbalance  the 
tilting  of  the  image  resulting  directly  from  the  disability  of  the 
inferior  rectus. 

We  cannot  place  this  important  part  of  the  subject  in  better  light 
than  by  quoting  from  Mauthner  the  rules  in  these  cases.  "In  gen- 
eral," says  this  learned  author,  "if  in  paralysis  of  a  muscle  acting  in 
a  vertical  direction,  the  distance  in  the  height  of  the  double  images 
increases  in  that  diagonal  position  in  which  the  paralyzed  eye  is  found 
in  the  outward  position  (position  of  abduction),  but  decreases  in  that 
diagonal  position  in  which  the  paralyzed  eye  stands  in  the  inward  posi- 
tion (position  of  adduction),  then  the  rectus  superior  or  rectus  in- 
ferior is  affected  by  the  paralysis,  no  matter  whether  the  double 
images  are  crossed  or  honwnymous,  and  independent  of  the  state- 
ment of  the  patient  that  he  sees  no  obliquity  of  the  images." 

So  on  the  other  hand  "the  difference  in  height  of  the  double 
images  in  paralysis  of  an  oblique  will  be  greatest"  when  the  paralyzed 
eye  is  rotated  inward  and  least  when  turned  outward.  "From  the 
different  behavior,"  adds  the  author,  "of  the  difference  in  height  of 
the  double  images  in  the  diagonal  position  rests  the  only  sure  differ- 
ential diagnostic  factor  between  paralysis  of  the  rectus  superior  and 
the  inferior  oblique,  on  the  one  hand,  and  the  rectus  inferior  and  the 
superior  oblique,  on  the  other." 

PARALYSIS  or  THE  INFERIOR  OBLIQUE. 

Except  that  the  diplopia  occurs  in  the  upper  part  of  the  field  of 
regard  and  that  the  image  should  tilt  with  its  upper  end  toward  the 
temple,  what  has  been  said  in  regard  to  paralysis  of  the  superior 
oblique  may  apply  to  the  diplopia  arising  from  paralysis  of  the  in- 
ferior oblique.  In  the  case  of  the  latter  muscle  the  image  of  the 
affected  eye  is  higher  than  the  other;  the  image  of  the  right  eye  is 
at  the  right  of  that  of  the  left  eye.  The  separation  of  the  images 
increases  as  the  eye  is  turned  inward  and  the  tilting  is  less. 


PARALYSIS    OF  INFERIOR  OBLIQUE.  465 

Paralysis  of  the  inferior  oblique  as  an  isolated  affection  is  an 
extremely  rare  form  of  paralysis.  Of  several  published  cases  which 
I  have  examined  with  care  the  majority  at  least  must  be  rejected  as 
not  being  true  examples  of  the  affection.  Curiously  enough  the  cases 
which  have  been  reported  in  greatest  detail  and  with  most  intelli- 
gence are  those  which  are  the  most  readily  rejected.  Graefe  did  not 
find  a  case  in  40,000  eye  cases,  and  Mauthner,  in  a  still  greater  num- 
ber of  cases,  found  no  instance  of  paralysis  of  the  inferior  oblique. 

It  cannot  be  said,  however,  that  this  is  never  an  isolated  affec- 
tion. 

The  indications  are  somewhat  similar  to  those  of  paralysis  of 
the  superior  oblique.  There  is  the  confusion  and  nausea,  the  false 
projection,  but  only  in  the  upper  part  of  the  field  of  regard,  and 
therefore  less  constantly  present  than  in  paralysis  of  the  superior 
oblique.  In  some  respects  this  confusion  in  the  upper  part  of  the 
visual  field  is  even  more  troublesome  than  that  in  the  lower  half,  for 
buildings  seem  to  be  falling  over  and  the  universe  appears  unsettled. 
Even  some  years  of  experience  may  not  relieve  the  patient  of  these 
unpleasant  apprehensions  respecting  the  stability  of  things.  The 
confusion  is  in  looking  up  and  to  the  side  of  the  affected  eye.  The 
classical  leaning  of  the  object  may  not  exist  in  looking  straight  for- 
ward; indeed,  the  leaning,  owing  to  a  normal  declination  of  one  or 
both  eyes,  may  be  exactly  opposite  that  which  is  shown  in  the  dia- 
grams of  the  text-books  as  the  leaning  from  paralysis. 

The  better  to  determine  the  relative  position  of  the  image  per- 
taining to  each  eye  it  is  well  to  introduce  a  contrast  of  color;  thus, 
a  red  glass  placed  before  one  eye  while  the  patient  looks  at  a  candle 
flame  will  enable  the  examiner  to  locate  without  trouble  the  position 
of  the  image  of  each  eye. 

The  relative  positions  of  the  double  images  may  be  summed  up 
in  the  following  analytical  key.1 


1  Modified  from  an  article  by  the  author  in  the  Ophthalmic  Record,  July, 
1894. 

30 


466  COLYTKOPIA. 

SECTION  LXIII. 

RELATIONS  OF  THE  DOUBLE  IMAGES  IN  PARALYSIS  OF  THE 
OCULAR  MUSCLES. 

(A)  DirLOPiA    CAUSED   BY   LATERAL   EOTATIONS    IN    THE 
HORIZONTAL  PLANE. 

1.  Images  liomonymous,  paralysis  of  the  external  rectus  of  the 
eye  toward  Avhich  the  rotations  cause  the  greatest  separation  of  the 
images. 

2.  Images   crossed,  paralysis  of  the  internal  rectus  of  the  eye 
toward  which  the  rotations  cause  the  least  separation. 

(13)  DIPLOPIA   INDUCED   BY   KOTATIONS   ABOVE   THE 
HORIZONTAL  PLANE. 

The  higher  image  belongs  to  the  affected  eye. 

1.  Images  separating   as   the   affected   eye   rotates   to   the  nose, 
paralysis  of  an  inferior  oblique. 

2.  Images  separating  as  the  eye  rotates  toward  the  temple,  paral- 
ysis of  a  superior  rectus. 

(C)  DIPLOMA  INDUCED  BY   VERTICAL  EOTATIONS   BELOW 

THE  HORIZONTAL  PLANE. 
The  lower  image  belongs  to  the  affected  eye. 

1.  Images  separating  when  the  affected  eye  turns  in,  paralysis 
of  the  superior  oblique. 

2.  Images  separating  as  the  affected  eye  turns  out,  paralysis  of 
the  inferior  rectus. 

According  to  the  rule,  in  B\  and  C*l  the  images  should  be  homon- 
ymous,  and  in  B2  and  C2  they  should  be  crossed.  In  the  first  and 
second  instances  a  normal  condition  represented  by  exophoria  may 
render  the  images  crossed,  while  in  the  case  of  B2  and  C2,  a  condition 
in  which  esophoria  is  a  manifestation,  there  may  be  liomonymous 
diplopia.  (See  diagrams  on  next  page.) 

SECTION  LXIY. 

OBJECTIVE  MANIFESTATIONS  OF  PARALYSIS  OF  THE  OCULAR 

MUSCLES. 

Beside  the  subjective  manifestations  of  paralysis  of  the  eye  mus- 
cles, vertigo,  confusion,  vitiated  orientation,  and  diplopia,  there  are 
certain  objective  phenomena  which  demand  attention. 


DIAGRAM  OF  FORMS  OF  DIPLOPIA. 


467 


The  pose  of  the  head,  to  which  reference  has  already  been  made, 
is  characteristic  for  most  forms  of  ocular  muscle  paralysis.  Thus, 
with  paralysis  of  a  lateral  muscle,  the  head  is  carried  to  one  side  in 


INTERNUS. 


EXTERNUS. 


SUPERIOR. 

r 


INFERIOR. 


SUP.    OBLIQ. 


\ 


Fig.  180. =Diagram  Indicating  the  Eelative  Positions  of  the  Images  in 
Paralysis  of  Individual  Muscles  of  the  Right  Eye.  Image  of  Right  Eye  Indi- 
cated by  the  Red  Line. 


468  COLYTROPIA. 

order  to  relieve,  as  far  as  possible,  the  occasion  for  bringing  into 
action  the  affected  muscle.  In  case  of  paralysis  of  a  superior  rectus 
the  chin  is  elevated,  and  when  both  superior  recti  are  disabled,  the 
head  is  held  very  far  back,  turning  neither  to  one  side  nor  the  other. 
With  paralysis  of  a  superior  ob-lique,  the  head  is  turned  downward 
and  in  the  direction  of  the  sound  eye. 

Secondary  deviation  is  conspicuous  in  paralysis  of  certain  mus- 
cles, but  not  very  prominently  shown  in  others.  For  example,  in 
slight  cases  of  paralysis  of  the  superior  oblique  scarcely  any  secondary 
deviation  is  to  be  observed,  while  in  even  moderate  paralysis  of  an 
external  rectus  the  secondary  deviation  is,  in  most  cases,  plainly  to  be 
seen. 

In  the  case  of  the  ordinary  concomitant  strabismus,  if  the  pa- 
tient fixes  one  eye  upon  a  distant  object  the  other  turns  in  (or  out). 
If,  in  a  case  of  ordinary  concomitant  converging  strabismus  the  test 
for  "deviation  in  exclusion"  is  made  and  repeated  several  times,  and 
the  extent  of  turning  of  each  eye  is  carefully  noted,  it  will  be  seen 
that  the  turning  of  the  usually  fixing  eye  when  behind  the  card  is 
exactly  or  very  nearly  the  same  in  extent  as  the  turning  of  the  usually 
squinting  eye,  and  that  as  the  card  is  passed  from  one  side  to  the 
other  the  same  amount  of  deviation  is  seen,  no  matter  before  which 
eye  the  card  is  found.  The  deviation  of  the  usually  squinting  eye  is 
called  the  "primary  deviation/'  while  that  which  occurs  when  the 
card  is  slipped  before  the  usually  straight  eye  is  known  as  the  "sec- 
ondary deviation/' 

Now  this  "secondary  deviation"  in  case  of  paralysis  is  quite  a 
different  matter  from  that  which  we  have  just  described  as  occurring 
in  the  common  form  of  squint. 

If  we  place  the  patient  with  a  paralysis,  for  example,  of  the 
external  rectus  of  the  right  eye,  facing  a  candle  situated  at  some  feet 
in  front,  it  will  be  seen  that  the  left  eye  fixes  the  flame  of  the  candle 
while  the  right  turns  toward  the  nose.  If  now  we  pass  the  little 
card  in  front  of  the  left  eye,  the  right  eye  will  move  by  jerks 
perhaps  outward  to  the  sagittal  plane  of  the  eye,  or  a  little  short  of 
it.  At  the  same  time  the  sound  eye  will  make  the  excursion  inward, 
but  not  as  in  the  other  case,  for  it  will  now  go  very  much  further 
than  the  right  eye  turned  in.  In  other  words,  the  "secondary"  devia- 
tion in  case  of  paralysis  exceeds,  and  generally  greatly  exceeds,  the 
primary  deviation.  This  is  an  important  element  in  the  diagnosis 
of  a  paralytic  squint. 


LIMITATION   OF  ACTION.  469 

SECTIOX  LXV. 

LIMITATION  OF  ACTION  OF  THE  PARALYZED  MUSCLE. 

If  the  patient  with  paralysis  of  the  external  rectus  of  the  right 
eye  is  asked  to  look  at  an  object  held  in  front  of  him,  a  pencil  for 
example,  and  directed  to  follow  the  object  with  his  eyes  as  it  is 
moved,  it  will  be  seen  that  as  the  pencil  is  moved  to  the  left  the  two 
eyes  will  follow  it,  the  right  probably,  especially  when  the  pencil  is 
only  a  little  to  the  left,  starting  farther  to  the  left,  but  gradually 
coming  to  fix  at  the  same  point  on  the  pencil.  If,  on  the  other  hand, 
the  pencil  is  moved  toward  the  right,  the  right  eye,  while  lagging 
behind  the  other,  will  still,  as  the  pencil  moves  beyond  the  median 
plane  toward  the  right,  follow  until  it  looks  straight  forward.  Then 
it  stops,  and  while  the  left  eye  will  continue  to  rotate  so  as  to  follow 
the  object,  the  right  eye  remains  fixed  in  its  position.  This  deviation 
of  the  eye  while  in  a  state  of  repose  and  the  sudden  arrest  of  move- 
ment when  it  has  reached  the  point  at  which  the  aid  of  the  affected 
muscle  is  demanded  in  order  to  carry  it  further,  constitute  the  most 
striking  objective  features  of  fresh  cases.  There  are  cases,  however, 
especially  of  paralysis  of  the  external  rectus  dating  from  early  in- 
fancy, in  which  the  affected  eye  has  no  squint  when  looking  straight 
forward;  it  is  only  when  the  object  looked  at  is  at  the  same  side  as 
the  affected  muscle  that  any  appearance  of  a  want  of  harmony  be- 
tween the  two  eyes  is  observed.  Whether  these  cases  can  be  regarded 
as  cases  of  true  paralysis  will  be  discussed  in  another  section. 


SECTION  LXVI. 

MEASUREMENT  OF  THE  DEVIATIONS  OF  PARALYSIS. 

To  determine  the  extent  of  the  deviations  from  paralysis  of  the 
eye  muscles  many  methods  have  been  suggested.  Locating  the  posi- 
tion of  the  images  as  they  appear  on  the  surface  of  a  wall  divided  by 
lines  of  latitude  and  longitude,  measurement  by  an  instrument  called 
a  strabismometer,  etc.  It  has  been  customary  with  writers  to  advise 
the  use  of  the  perimeter,  and  in  1886  I  devised  a  method1  of  this 


1  On  the  arc  of  the  perimeter  a  rider  projecting  above  the  arc  is  movable, 
and  while  one  eye  is  directed  across  the  center  of  the  perimeter  toward  the  dis- 
tant object,  the  movable  rider  can  be  moved  so  as  to  obstruct  the  deviating 
image.  The  perimeter  registers  the  distance  in  degrees  between  the  images. 


470  COLYTROPIA. 

kind  which  I  thought  less  faulty  than  others.  The  method  is,  how- 
ever, at  best  clumsy,  rather  troublesome,  and  above  all,  not  of  great 
utility.  It  is,  however,  as  good  as  any  of  its  kind. 

The  measurement  of  diplopia,  which  is  most  convenient  and 
most  likely  to  give  uniform  results  when  proper  conditions  are  ob- 
served, is  that  which  can  be  made  by  prisms. 

Xo  measurements  of  the  deviations  are  in  fact  entirely  satisfac- 
tory, for  these  ma)"  vary  from  hour  to  hour. 

The  method  of  estimating  the  real  extent  of  disability  of  the 
affected  muscle  is  that  of  determining  the  rotating  ability  of  the 


Fig.    181. — Arm  of   Stevens's   Perimeter.     The   rider   at   H'   obscures  the 
flame  at  (t  and  then  at  b,  the  perimeter  registering  the  angular  distance. 

muscle.  The  tropomcter  affords  a  perfect  means  of  accomplishing 
this  with  no  especial  difficulty,  and  by  its  means  it  is  easy  to  ascer- 
tain, as  treatment  goes  on,  whether  the  muscle  is  acquiring  more 
rotating  ability  or  is  remaining  stationary. 


SECTION  LXVIL 

NUCLEAR  PARALYSIS. 

Paralysis  of  independent  muscles  occurs  from  causes  which  may 
affect  only  the  branch  of  nerve  supplying  that  muscle  or  the  more 
minute  divisions  of  it  which  are  distributed  to  its  parts;  or,  again, 
the  cause  may  be  found  far  behind  these  more  immediate  nerve 
branches.  When  several  muscles  are  affected  at  the  same  time  in 
cases  in  which  no  mechanical  obstruction  exists,  we  must,  in  general, 
look  for  the  seat  of  trouble  at  a  point  so  far  back  that  all  the  nerves 
affected  may  be  influenced  by  the  same  cause. 

In  the  forms  of  disability  known  as  ophthalmoplegia  the  nerves 


NUCLEAR  PARALYSIS.  471 

supplying  several  muscles  may  be  subject  to  a  common  disabling 
influence,  and  hence  the  conditions  of  paralysis  are  usually  not  as 
simple  as  those  which  have  been  discussed. 

Ophthalmoplegia,  when  it  involves  only  the  external  eye  mus- 
cles, is  known  as  ophthalmoplegia  externa.  When  it  involves  only 
those  which  are  within  the  eyeball  (constrictor  of  pupil,  accommo- 
dation, tensor  choroidse)  it  is  called  ophthalmoplegia  interna,  but  if 
both  these  groups  of  muscles  are  involved,  it  is  total  ophthalmoplegia.1 

In  ophthalmoplegia  externa,  when  more  than  a  single  muscle  is 
affected,  the  limitation  of  movements  is,  of  course,  in  the  direction 
of  the  action  of  all  the  muscles  affected.  Hence,  while  the  princi- 
ples which  have  already  been  announced  as  applying  to  the  diplopia 
and  restriction  of  mobility  in  case  of  paralysis  of  individual  mus- 
cles holds  good,  the  sum  of  the  corresponding  phenomena  in  case  of 
multiple  paralysis  is  more  complicated. 

In  order  to  arrive  at  a  clear  understanding  of  nuclear  paralysis 
it  is  important  to  recall  the  anatomical  facts  regarding  the  nuclear 
origins  of  the  nerves  governing  the  movements  of  the  eye  muscles  as 
they  are  shown  in  Section  VIII  to  Section  X. 

We  may  here  summarize  these  facts  as  follows: — 

Lying  in  the  mid-brain,  in  the  region  of  the  anterior  quad- 
rigeminal  bodies,  in  the  floor  of  the  aqueduct  of  Sylvius  at  the  right 
and  left  of  the  median  line,  are  groups  of  cells  extending  backward 
about  6  millimeters  (Bernheimer),  which,  when  cut  by  a  transverse 
section  from  above  downward,  show  an  oval  outline  of  the  section, 
the  two  halves  of  the  section  looking  like  two  eggs  with  the  small 
ends  down  and  the  upper  ends  somewhat  diverging,  the  small  ends 
resting  upon  the  posterior  longitudinal  bundle,  and  which  together 
constitute  the  nuclear  origin  of  the  different  branches  of  the  oculo- 
motor or  third  nerve.  Immediately  behind  this  pair  of  groups  is 
another  pair  so  closely  associated  with  the  first  that,  according  to 
most  of  the  authorities,  it  is  only  by  the  difference  in  the  size  of  the 
cells  and  the  course  of  its  fibers2  that  the  boundary  can  be  well  made 
out,  and  which  has  an  extent  considerably  less  than  the  first  pair. 
This  posterior  pair  of  cell  masses  constitutes  the  origin  of  the  fourth 
pair  of  nerves. 


1  Jonathan   Hutchinson,   Lancet,    1879,   also   Medico-Chirurgical   Transac- 
tions, 1879. 

2  Bernheimer  states  that  the  difference  in  character  of  the  cells  does  not 
constitute  a  mark  of  distinction,  but   that  the  course   of  the  fibers   plainly 
distinguishes  the  two  groups  (Das  Wurzelgebiet  des  Oculomotorius). 


472  COLYTROPIA. 

At  some  distance  behind  the  last  is  found  another  pair  of  cell 
groups  from  which  arise  the  fibers  which  go  to  make  the  sixth  nerves. 

From  the  mass  composing  the  nucleus  of  the  oculo-motor  nerve 
arise  the  fibers  which,  after  passing  forward  and  downward,,  first 
unite  in  a  number  of  bands  of  nervous  fibers  and  finally  join  in  a 
single  trunk  as  the  third  cranial  nerve  to  supply  the  muscle  of  ac- 
commodation and  of  the  sphincter  of  the  iris  within  the  eye,  and  the 
elevator  muscle  of  the  upper  lid,  the  superior  rectus,  the  internal 
rectus,  the  inferior  oblique,  and  inferior  rectus,  exterior  to  the  eye- 
ball, the  fibers  for  these  various  nerves  being  in  relation  to  the  various 
parts  of  the  nuclear  mass  in  the  order  from  before  backward  as  they 
have  been  above  mentioned. 

To  summarize  the  most  recent  results  of  investigations  upon  apes 
by  Bernheimer1  in  regard  to  the  origin  of  the  fibers  of  the  branches- 
of  the  oculo-motor  nerve  directed  to  the  exterior  muscles,  it  is 
found : — 

1.  The  nuclear  field  of  the  levator  palpebra3  superioris  lies  in 
the  anterior  part  of  the  nuclear  mass   (but  behind  the  part  belong- 
ing to  the  ciliary  and  iris  muscles)    and  in  the  middle  and  dorsal 
portion  of  that  part,  its  fibers  proceeding  directly  to  the  nerve  on 
the  same  side  with  the  origin. 

2.  Behind  this  cell  group  is  that  belonging  to  the  superior  rectus, 
its  fibers  also  preceding  to  the  nerve  stem  of  the  same  side  as  the 
origin  cells. 

3.  Somewhat  medianward  and  behind  the  last  group  lies  the 
group  supplying  the  fibers  for  the  internal  rectus,  some  of  which  pass 
directly  to  the  nerve  of  the  same  side  and  some  of  which  cross  to  the 
opposite  nerve  stem. 

4.  The  cell  group  for  the  inferior  oblique  lies  outward  and  be- 
hind that  for  the  internal  rectus,  and  the  fibers  from  this  center  cross 
to  the  opposite  nerve. 

5.  The  inferior  rectus  nerve  arises  from  a  group  posterior  to  and 
somewhat  overtopping  the  inferior  oblique  group,  and  its  fibers  cross 
to  the  opposite  nerve. 

Behind  these  parts  of  the  mass  composing  the  oculo-motor  nu- 
cleus is  the  nucleus  of  the  trochlear  (fourth)  nerve,  whose  fibers  cross 
to  the  opposite  side,  while  the  nuclear  mass  for  the  sixth  nerve  is 
considerably  behind  these,  in  the  floor  of  the  fourth  ventricle,  with. 


1Archiv  fur  Ophthalmol.,  Bd.  xliv,  3,  481. 


NUCLEAR  PARALYSIS. 


473 


fibers  passing  directly  to  the  nerve  of  the  same  side,  no  intercrossing 
having  been  recognized.  Notwithstanding  the  results  of  all  investi- 
gations it  is  to  be  borne  in  mind  that  the  exact  boundaries  of  these 
nuclear  centers  are  still  in  suspense. 

While  bearing  in  mind  the  location  and  relative  position  of 
these  nuclear  masses  it  is  important  to  note  also  the  peculiarities  of 
the  mid-brain,  the  region  in  which  these  nuclear  groups  are  found. 

The  region  receives  its  nourishing  arteries1  from  the  basilar 
trunk  of  the  posterior  cerebral  artery.  [See  Fig.  27,  page  85.]  This 
arterial  trunk  lies  in  the  depression  at  the  median  line  of  the  pons 


Tr. 


Fig.  182. — Professor  Bernheimer's  Diagram  of  the  Nucleus  of  the  Oculo- 
motor and  of  the  Trochlearis  Nerve.  (By  permission  of  Professor  Bern- 
heimer.) 

Varolii,  extending  to  the  medulla  oblongata,  where  it  divides.  In 
its  course  it  sends  directly  into  the  deeper  structures,  in  which  lie  the 
nuclear  centers  for  the  eye  muscles  as  well  as  some  other  nuclei,  a  large 
number  of  branches  which  run  in,  nearly  parallel  directions  and  which 
penetrate  to  the  region  of  the  various  nuclear  masses  for  the  eye  mus- 
cles as  well  as  to  those  for  the  facial  and  fifth  nerve.  These  median 
arteries  do  not,  like  many  small  arteries,  anastomose  freely  with  each 
other,  but  run  independently  to  their  destination.  It  will  be  seen  that 


1  According  to  D'Astros  (Neurol.  Centralbl.,  1894,  Nos.  21,  22)  the  entire 
blood  supply  of  the  oculo-motor  group  is  from  these  arteries. 


474  COLYTROPIA. 

this  peculiar  arrangement  may  have  an  extremely  important  bearing 
upon  the  pathology  of  the  region  supplied  by  them ;  for  since  -each 
vessel  furnishes  the  supply  of  blood  to  its  particular  field  independent 
of  the  other  vessels  of  the  series,  it  follows  that  an  obstruction  of  any 
one  or  two  of  these  small  arteries  may  induce  degeneration  of  the  part 
which  it  should  supply,  and  hence,  too,  a  pathological  process  which 
advances  along  the  course  of  the  basilar  artery,  even  while  it  may 
not  obstruct  the  artery  itself,  may  affect  progressively  one  after  an- 
other of  these  median  arteries  so  as  to  induce  progressively  degenera- 
tion of  one  after  another  of  the  nuclei  supplied,  thus  paralysis 
of  one  muscle  or  set  of  muscles  succeeding  another  in  regular  order. 
Hence,  the  locations  of  the  nuclear  masses  in  the  mid-brain  furnish 
the  elements  of  the  picture  of  many  affections  in  which  the  more 
general  symptoms  of  central  nerve  degeneration  are  associated  with 
paralysis  of  one  or  more  of  the  eye  muscles. 

The  question  of  a  nuclear  center  for  the  conjugate  side  move- 
ments of  the  eyes  is  far  from  being  satisfactorily  settled,  and  it  would 
appear  not  to  be  a  question  of  importance  in  this  connection,  since  a 
cortical  center  for  coordinating  such  actions  would  seem  quite  to  an- 
swer the  demands.  So  also  the  centers  which  some  have  assumed  on 
the  hypothesis  that  there  should  be  a  controlling  region  for  convergence, 
and  even  for  divergence,  would  seem  not  to  be  required  by  physiolog- 
ical or  pathological  facts.  Mobius  suggests  several  connecting  media 
between  the  cortex,  the  abducens  nucleus,  and  nuclei  of  nerves  govern- 
ing convergence,  but  he  has  not  located  these  connecting  media. 

From  the  foregoing  considerations  it  will  be  seen  that  a  disease, 
a  pressure,  a  degeneration,  or  a  failure  of  nutrition  affecting  one  or 
more  of  the  regions  in  which  lie  these  three  masses  of  nuclear  cells 
may  be  expected  to  result  in  a  disability  of  the  muscle  or  muscles 
respectively  dependent  upon  these  groups  for  the  nerve  impulse  nec- 
essary for  voluntary  motion. 

The  nuclear  mass,  disease  of  which  may  affect  the  largest  num- 
ber of  muscles,  is  that  which  lies  most  anteriorly  and  is  of  itself  the 
largest,  the  oculo-motor  nucleus  or  nucleus  of  the  third  nerve. 

NUCLEAR  PARALYSIS  OF  THE  OCULO-MOTOR  NERVE. 

The  nucleus  may  be  affected  in  only  a  part  of  the  cells  or  the 

whole  mass  may  be  involved  in  the  disease.     In  the  first  condition 

only  one  or  two  muscles  or  one  or  two  pairs  of  muscles  may  be 

affected.     It  is  rare  that  a  single  muscle  is  disabled,  yet  such  single 


TOTAL  OCULO-MOTOR  PARALYSIS.  475 

paralyses  occur  from  disease  in  or  near  this  nucleus.  In  case  the 
whole  or  a  great  part  of  the  nuclear  mass  is  involved  in  the  affection, 
all  the  muscles  controlled  by  the  third  nerve  will  be  disabled. 

In  the  latter  instance  we  have  a  case  of  total  oculo-motor  paral- 
ysis. 

TOTAL  OCCLO-MOTOR  PARALYSIS. 

The  picture  of  total  oculo-motor  paralysis  is  striking  and  char- 
acteristic, since  not  only  four  of  the  muscles  which  move  each  eye, 
but  also  the  elevator  of  the  lid,  the  muscle  of  accommodation,  and 
that  governing  the  pupil  are  involved  in  the  trouble. 

The  symptom  which  first  attracts  the  notice  of  the  observer, 
and  that  which  is  frequently  the  first  observed  by  the  patient,  is  the 
drooping  of  the  upper  lid  and  the  necessity  of  making  a  strenuous 
effort  to  uncover  the  eye,  or  the  raising  of  the  chin  so  as  to  permit 
the  eye  to  see  under  the  border  of  the  lid. 

Even  in  complete  forms  of  the  levator  palpebra?  superioris 
the  lid  can  be  to  some  extent  raised,  since  the  frontal  muscle  above 
the  orbit  exerts  its  influence  in  raising  the  brow  as  well  as  the  lid. 
By  this  action  of  the  frontalis  the  peculiar  and  characteristic  expres- 
sion of  paralysis  ("the  Hutchinson  expression")  is  given. 

The  second  symptom,  that  which  is  greatly  troublesome  to  the 
patient,  is  the  disability  of  the  muscles  which  move  the  eyes  up  and 
down  and  toward  the  nose.  The  superior  rectus,  the  inferior  rectus, 
the  internal  rectus,  and  the  inferior  oblique  are  all  disabled.  The 
external  rectus  and  the  superior  oblique  continue  to  act. 

The  eye  cannot  turn  in  beyond  the  median  line ;  it  can  only  turn 
down  as  it  is  rotated  by  the  superior  oblique  and  the  upward  rotation 
is  absent. 

The  action  of  the  two  remaining  muscles  can  be  well  observed 
in  a  case  in  which  the  paralysis  of  the  oculo-motor  nerve  is  total. 
The  eye  is  rotated  out  and  the  upper  part  of  the  vertical  meridian  is 
rotated  in.1 

The  patient  will  have  diplopia  which  will  occur  especially  when 
attempting  to  read  and  the  images  will  be  crossed.  In  general  the 
images  are  not  level  even  when  the  oculo-motor  nerve  of  each  eye  is 
affected,  since  the  degree  of  paralysis  is  liable  to  be  unequal.  Hence, 


1  Mauthner,  p.  297,  says  that  the  meridian  is  rotated  out,  which  is  an 
error. 


476 


COLYTROPIA. 


the  images  may  separate  vertically  when  the  attempt  is  made  to  look 
up  or  down. 

Owing  to  the  implication  of  the  nerve  governing  the  contraction 
of  the  pupil  the  pupillary  opening  is  large,  although  not  dilated  to 
the  full  extent,  and  it  does  not  respond  to  the  stimulus  of  light.  The 
accommodation  is  also  suspended. 

In  a  considerable  proportion  of  cases  in  which,  while  all  the 
motor  muscles  governed  by  the  third  nerve  are  disabled,  the  nerve 
branches  supplying  the  interior  muscles,  sphincter  of  the  pupil,  ten- 
sor choroida?,  and  accommodation,  may  continue  to  perform  their 
functions  normally,  hence,  when  the  affection  extends  to  the  external 


Fig.  183. — Ophthalraoplegia  Externa  in  an  Adult. 

muscles  only  it  is  known  as  oplitlialmoplegia  externa,  when  involving 
only  the  internal  muscles  it  is  ophthalmoplegia  interna,  and  when 
including  both  the  external  and  internal  muscles  it  is  called  total 
oplitlialmoplegia.  So  while  the  accommodation  is  preserved,  the 
action  of  the  pupil  may  react  to  the  impulse  of  accommodation,  while 
it  is  unaffected  by  the  action  of  light.  In  certain  cases  the  pupil  is 
contracted. 

Similar  considerations  also  show  that  with  an  affection  of  a 
part  or  of  all  of  the  branches  of  the  third  nerve,  the  fourth  nerve, 
whose  nuclear  cells  join  those  of  the  third  nerve,  may  escape,  while 


OPHTHALMOPLEGIA   EXTERNA.  477 

the  sixth  nerve,  whose  nuclear  group  is  situated  considerably  further 
back,  may  participate  in  the  affection. 

On  the  other  hand  the  whole  line  of  nuclear  masses  may  be 
affected  as  in  the  following  case: — 

Dr.  B.,  aged  62,  in  1889,  had  an  attack  of  motor  aphasia  which  followed 
the  extraction  of  a  tooth.  The  attack  lasted  thirty-six  hours  and  was 
followed  by  weakness  and  drowsiness.  After  some  weeks  he  appeared  to  be 
well.  Early  in  1892  he  had  occasional  attacks  of  diplopia  which,  after  a 
fatiguing  journey,  became  permanent.  With  more  pronounced  symptoms  of 
double  vision  ptosis  of  both  sides  was  associated. 

He  was  examined  by  me  in  June,  when  his  conditions  were  as  follows:  — 

Has  had  no  symptoms  of  mental  disturbance,  memory  good.  Is  in  other 
respects  in  fair  health.  Appears  like  a  robust  man,  but  the  patellar  reflexes 
are  absent.  Xo  history  of  specific  disease. 

Vision  Vis  each  eye  with  sph.  +  1.25.  Can  read  with  sph.  +  3.50  either 
eye,  but  can  only  do  so  by  covering  the  other  eye.  Both  discs  hypersemic. 
Field  of  vision  each  eye  normal.  Brows  strongly  arched  (see  Fig.  183,  p.  476) 
and  the  skin  of  the  forehead  is  in  deep  folds.  Ptosis  well  marked.  The  right 
eye  has  no  rotation  outward,  but  rotates  in,  down  or  up  about  15°.  The  lefb 
eye  has  similar  restrictions,  except  that  the  outer  rotation  is  about  20°.  In 
none  of  the  movements  is  marked  torsion  to  be  observed.  Pupil  responsive 
to  light.  Looking  at  candle  flame  at  6  meters  there  is,  in  primary  position, 
homonymous  diplopia. 

Looking  at  object  15°  below  horizon  right  eye  image  directly  above. 

Looking  at  object  15°  above  horizon  right  eye  image  directly  below. 

Object  15°  to  left,  vertical  diplopia,  right  eye  image  above. 

Object  15°  to  right,  homonymous  diplopia,  images  always  erect  and  paral- 
lel; at  near  points  images  crossed. 

This  gentleman  after  the  free  use  of  iodide  of  potassium  for  some 
weeks  was  able  to  get  single  vision  at  all  points  within  a  somewhat  restricted 
field.  He  died  a  year  later  from  pneumonia. 

Paralysis  from  disease  of  the  nuclear  mass  of  the  sixth  nerve 
manifests  itself  clearly  in  contrast  to  other  nuclear  disturbances, 
since  this  nucleus  controls  but  a  single  nerve,  and  that  governs  the 
rotation  of  the  eye  out.  It  is  not  so  clearly  differentiated  from  paral- 
ysis of  the  nerve  branch  within  the  orbit.  The  conspicuous  symptom 
then  will  be  a  converging  squint.  Other  symptoms,  such  as  the 
diplopia,  the  secondary  deviation,  etc.,  will  readily  suggest  them- 
selves. 

Since  the  indications  of  paralysis  of  the  fourth  nerve  present 
some  exceptions  to  the  general  rules,  it  will  not  be  so  easy  in  every 
instance  to  locate  the  disturbance.  In  this  case  there  is  no  deviation 
of  the  eye  such  as  to  attract  attention,  and  often  it  is  so  slight  as  not 


478 


COLYTROPIA. 


to  be  clearly  made  out,  even  when  it  is  looked  for.  The  diagnostic 
indications  are  shown  at  page  466. 

The  question  of  the  exact  locality  of  the  disease  in  a  case  of 
nuclear  paralysis  of  the  fourth  nerve  is  one  to  which  investigators 
have  not  always  given  the  same  answer. 

Xot  a  few  cases  arc  on  record  in  which  a  one-sided  paralysis 
of  all  of  the  exterior  muscles  supplied  by  the  third  nerve,  with  per- 
haps the  addition  of  the  external  rectus  and  the  superior  oblique, 
that  is,  all  of  the  muscles  of  the  same  eye,  have  been  affected. 

When  the  crossing  of  the  fibers  of  the  fourth  nerve  is  consid- 
ered, it  is  apparent  that  should  such  a  combination  of  paralyses  be 


Fig.  184. — Paralysis  of  the  Third  Nerve  in  a  Child. 

found,  either  the  disease  is  not  nuclear  or  it  must  have  attacked  the 
opposite  side  when  reaching  the  posterior  boundary  of  the  third 
nerve  group,  and  then  have  returned  to  the  first  side  of  that  group 
when  reaching  that  of  the  sixth  nerve,  a  supposition  most  improb- 
able ;  or  it  must  be  assumed,  contrary  to  the  observations  of  anatom- 
ists, that  the  fibers  of  the  trochlearis  (fourth  nerve)  arise  from  the 
same  side  as  the  eye  supplied. 

Mauthner1  adopts  this  conclusion,  and  declares : — 
"On  the  ground  of  clinical  observations  I  am  of  the  opinion 
that  the  nerves  for  the  eye  musculature  of  each  eye  all  have  their 
nuclei  on  the  same  side,  and  that  therefore,  the  one-sided  total  oph- 
thalmoplegia  is  conditioned  simply  by  the  progressive  disease  of  the 
nerve  nuclei  of  the  same  side." 


1  "Augenmuscle  Lahmungen,"  p.  368. 


CAUSES  OF  NUCLEAR  PARALYSIS.  479 

This  conclusion  of  the  learned  author  is  opposed  to  the  great 
body  of  anatomical  facts  as  they  have  been  presented  during  recent 
years  and  by  many  clinical  facts. 

As  a  most  important  fact  in  the  diagnosis  of  the  location  of  the 
disease  in  a  case  involving  the  fourth  nerve  and  the  branches  of  the 
third,  if  the  paralysis  is  all  on  the  same  side,  the  affection  is  not 
nuclear. 

A  nuclear  origin  may  be  with  some  certainty  assumed  under  the 
following  circumstances : — 

1.  Isolated  paralysis  of  the  accommodation  and  of  the  sphincter 
of  the  pupil  not  induced  by  drugs  applied  to  the  eye. 

2.  Paralysis  of  the  branches  of  the  third  nerve  distributed  to  the 
external  muscles  only. 

3.  Paralysis  of  some  of  the  branches  of  the  third  nerve  with 
paralysis  of  the  fourth  nerve  of  the  opposite  side.     This  speaks  both 
for  the  nuclear  origin  of  the  third  and  fourth  nerve  paralysis. 

Paralysis  of  nuclear  origin  may  affect  the  fourth  or  the  sixth 
nerve,  or,  indeed,  cither  of  the  nerves  supplying  an  external  muscle, 
but  the  nuclear  origin  of  the  paralysis  cannot  be  proven  in  the  ab- 
sence of  the  disability  of  a  branch  supplying  some  other  muscle  or 
muscles  except  as  it  may  be  assumed  in  connection  with  some  disease 
which  is  extremely  liable  to  induce  it.  For  example,  a  paralysis  of  the 
abducens  nerve  occurring  in  connection  with  tabes  may  be  assumed 
to  be  of  nuclear  origin.  It  might,  however,  even  in  this  case  be  of 
peripheral  origin,  but  the  well-known  fact  that  such  paralysis  is  a 
frequent  symptom  of  tabes  renders  the  diagnosis  of  nuclear  origin 
extremely  probable. 

SECTION  LXVIII. 
.    CAUSES  OF  NUCLEAR  PARALYSIS. 

^ETIOLOGICAL  CAUSES  or  THE  FIRST  CATEGORY. 

Turning  our  attention  now  to  the  causative  conditions  of  nuclear 
paralysis  we  recur  to  the  categories  of  Mauthner :  the  proximate  cause 
being  the  aetiological  factor  of  the  first  category.  Thus,  if  a  paralysis 
is  conditioned  on  compression,  the  compression  is  the  astiological 
moment  of  the  first  category.  The  aetiological  factor  of  the  second 
category  is  the  cause  of  the  factor  of  the  first  category;  thus,  if  a 
tumor  causes  the  compression  in  the  case  supposed,  the  tumor  is  the 
factor  of  the  second  category.  Finally  the  origin  of  this  factor  of 


480  COLYTROPIA. 

the  second  category  is  the  factor  of  the  third  category.  Continuing 
the  supposition  of  pressure  and  that  the  pressure  is  from  a  tumor, 
then,  if  syphilis  is  the  cause  of  the  tumor,  it  is  the  factor  of  the 
third  category. 

Thus,  if  the  paralysis  is  confined  to  the  intra-ocular  musculature, 
it  may  he  assumed  that  the  pressure,  hyperasmia,  or  other  factor  of 
the  first  category  is  located  toward  the  anterior  extremity  of  the 
nuclear  mass  for  the  third  nerve.  When  the  internal  rectus,  the  supe- 
rior and  inferior  recti,  and  the  inferior  oblique  are  involved  indepen- 
dently of  the  interior  muscles,  the  pressure  or  disease  is  located  fur- 
ther hack,  hut  in  front  of  the  nucleus  for  the  fourth  nerve.  If  all 
the  parts  supplied  hy  the  third  nerve,  interior  and  exterior,  are  in- 
volved, the  causative  factor  affects  both  the  anterior  extremity  and 
more  or  less  of  the  main  nuclear  mass. 

A  paralysis  of  all  the  exterior  muscles  supplied  by  a  third  nerve, 
while  the  interior  muscles  remain  intact,  does  not  necessarily  imply 
that  the  causative  factor  of  the  first  category  involves  the  body  of  the 
nucleus  of  the  third  nerve.  Professor  Frankl-Hockwart  reports  a  case 
in  which,  with  a  paralysis  of  all  the  motor  muscles  supplied  by  the  third 
nerve,  the  accommodation  and  pupil  movements  were  maintained  nor- 
mally.1 This,  according  to  the  generally  accepted  view,  would  indi- 
cate an  affection  or  a  pressure  upon  certain  and  only  certain  parts  of 
the  nuclear  mass  for  the  third  nerve. 

Autopsy  showed  no  affection  of  the  nucleus  or  ciliary  ganglion, 
hut  an  acute  interstitial  neuritis  of  the  trunk  of  the  third  nerve  in  its 
passage  at  the  base  of  the  cranium. 

Such  exceptional  cases  are  extremely  rare,  hut  should  caution 
against  too  positive  diagnosis. 

Paralysis  of  a  single  muscle  from  nuclear  affection  occurs  most 
frequently  in  the  external  rectus  or  superior  oblique.  Since  each  of 
these  muscles  is  supplied  from  a  separate  group  of  cells  it  is  easy  to 
see  how  an  individual  muscle  may  be  singled  out  for  disability.  When 
pairs  of  muscles  acting  in  the  same  lateral  direction  are  affected,  the 
others  remaining  intact,  there  must  naturally  be  difficulty  in  inter- 
preting the  character  of  the  nuclear  difficulty,  since  there  must  be 
a  region  of  the  nuclear  mass  which  is  unaffected  while  two  separated 
areas"  must  be  disabled.  When  two  muscles,  however,  each  acting 
vertically,  are  at  the  same  time  alone  affected,  it  is  less  difficult  to 


1  "Paralysis    of   Third    Xerve   from   Interstitial    Xeuritis."       Obersteiners 
Arbeiten  aus  den  Neurologischen  Institute.      IX  Heft,  1902. 


CAUSES  OF  NUCLEAR  PARALYSIS.  481 

suppose  that  the  disabling  factor  passes  from  one  to  the  other  side 
of  the  nuclear  mass.  Again,  when  from  nuclear  causes  muscles  of 
the  two  eyes  acting  diagonally,  as,  for  example,  the  right  superior 
and  the  left  superior  oblique,  we  have  again  a  pathological  problem 
of  much  intricacy  to  solve. 

J^TIOLOGICAL  FACTORS  OF  THE  SECOND  AND  THIRD  CATEGORIES. 

When  we  turn  to  this  category  a  very  considerable  array  of  causes 
is  to  be  considered.  It  is  unnecessary  to  discuss  each  separately  here 
or  even  to  enumerate  all  to  which  such  paralyses  have  been  attributed. 

It  is  well  known  that  nuclear  paralyses  are  often  associated  with 
tabes.  Attention  was  many  years  ago  called  to  this  by  Jonathan 
Hutchinson  and  is  now  commonly  observed.  It  is  an  important 
observation  that  for  the  majority  of  the  cases  it  is  only  the  exterior 
musculature  that  is  affected  with  tabes,  accommodation  and  pupil 
reflex  remaining  generally  intact  or  only  partially  disabled. 

The  findings  from  autopsies  have  usually  been  a  gray  degenera- 
tion of  the  nuclear  cells,  which  in  some  instances  have  been  almost 
entirely  replaced  by  connective  tissue.  Eeferring  to  Section  LXVII 
the  importance  of  the  blood-supply  to  the  nuclear  mass,  especially 
the  posterior  portion  of  it,  through  the  median  arteries  of  the  basilar 
trunk  of  the  posterior  cerebral  artery,  is  here  emphasized. 

Conditions  which  induce  atrophy  of  the  optic  nerves  often  also 
induce  atrophy  of  the  nuclear  cells. 

The  following  is  a  typical  illustration  of  paralysis  of  all  the 
branches  of  the  third  nerve  with  loss  of  sight  from  atrophy  of  the 
optic  nerve: — 

January,  1888,  Miss  K.,  aged  40,  had  been  subject  for  many  years  to 
headaches  of  intense  character.  She  had  taken  drugs  of  various  kinds  and  had 
resorted  to  other  expedients  with  no  relief  when,  five  years  ago,  she  became 
conscious  of  a  drooping  of  the  left  upper  lid.  She  soon  after  noticed  that 
although  she  could  read  to  herself  with  no  especial  difficulty,  if  she  attempted 
to  read  aloud  she  saw  double.  She  relinquished  her  occupation  and  rested, 
with  the  result  of  a  temporary  improvement,  but  two  years  ago  began  to  lose 
the  sight  of  the  left  eye,  and  its  movements  became  more  restricted. 

At  present  she  has  intense  pains  in  the  temples,  especially  in  the  left,  a 
sense  of  stiffness  about  the  left  eye  and  often  attacks  of  vertigo.  The  left 
eye  is  sightless  and  the  ophthalmoscope  shows  atrophy  of  the  nerve. 

Patient  rests  well  at  night,  but  as  soon  as  she  opens  the  eyes  in  the 
morning  pain  and  vertigo  commence  and  she  requires  a  long  time,  sometimes 
an  hour  or  more,  for  dressing. 

31 


482  COLYTROPIA. 

The  following  conditions  are  observed  in  respect  to  the  mobility  of  the 
eyes  and  their  surroundings:  — 

Right  eye,  rotations  normal.  Left  eye,  ptosis,  complete  so  far  as  the 
special  muscle  of  the  lid  is  concerned,  but  by  the  aid  of  the  frontal  muscle  she 
can  nearly  uncover  the  upper  half  of  the  cornea.  The  pupil  is  widely  dilated. 

The  eye  can  be  directed  toward  the  left  temple,  and  in  this  direction  it 
has  the  full  normal  excursion.  Can  carry  the  pupil  inward  as  far  as  the 
median  line,  but  no  further.  There  is  no  direct  upward  or  downward  move- 
ment, and  when  the  right  eye  rotates  directly  in  or  out  there  is  very  slight 
torsion.  When,  on  the  other  hand,  the  right  eye  moves  down,  the  left  eye 
performs  a  very  distinct  torsion,  the  upper  extremity  of  the  vertical  meridian 
of  the  cornea  moving  toward  the  median  plane  about  10°  of  arc,  and  the  eye 
turns  down  and  out.  There  is  a  slight  torsion  out  when  the  right  eye  is 
directed  upward.  Careful  examinations  were  made  of  the  movements  of  the 
cornea  by  the  aid  of  a  narrow  strip  of  white  paper  attached  to  the  lower  half 
of  the  cornea. 

It  is  evident  that  in  this  case  the  fourth  and  sixth  nerves  remained 
intact. 

Disseminated  sclerosis  of  the  brain  substance  might  readily  bring 
about  an  atrophy  of  the  optic  nerve  as  well  as  the  nucleus  of  the 
oculo-motor  nerves.  Dufour  mentions  two  cases  of  disseminated 
sclerosis  with  oculo-motor  paralysis,  from  the  experience  of  others. 

Nuclear  paralysis  is  associated  also  with  syringomyelia. 

It  is  evident  that  the  pressure  of  tumors  in  the  vicinity  of  the 
nuclear  mass  may  be  an  important  factor  in  the  induction  of  nuclear 
paralysis.  The  tumor  may  have  its  origin  in  the  white  substance,  in 
a  nerve  or  nerve  sheath  or  in  the  cortex.  In  18791  I  reported  a  case 
of  tumor  of  the  auditory  nerve  which  induced  paralysis  of  the  ex- 
terior and  interior  ocular  muscles. 

Tubercular  tumors  are  more  likely  than  others  to  induce  paral- 
ysis of  muscles  supplied  by  fibers  from  separated  areas  of  the  nuclear 
mass  by  affecting  isolated  parts  of  the  nuclear  mass. 

Gummata  from  syphilitic  affections  include  perhaps  the  greatest 
number  of  inducing  causes  of  nuclear  paralysis. 

As  these  tumors  are  located  in  so  many  parts  of  the  brain  sub- 
stance, and  as  they  are  of  more  frequent  occurrence  than  other  brain 
tumors,  it  is  not  surprising  that  the  suggestion  of  syphilitic  origin 
should  at  once  occur  in  a  case  of  ophthalmoplegia.  Since  many  other 
causes  contribute  to  the  sum  of  such  cases,  it  is  therefore  unjusti- 
fiable to  accept  the  suggestion  without  distinct  evidence. 


"Tumor  of  the  Auditory  Nerve  Occupying  the  Fossa  of  the  Cerebellum." 
George  T.  Stevens:     Archives  of  Otology,  vol.  viii,  p.  171,  1897. 


FASCICULAR  PARALYSIS.  483 

Haemorrhages  in  the  vicinity  of  the  nuclear  mass  may,  by 
pressure  or  by  isolating  it  from  the  cortex,  induce  paralysis  of  ocular 
muscles  with  or  without  hemiplegia.  Abscess  or  tubercle  may  also 
be  the  source  of  pressure. 

Infectious  diseases  sometimes  induce  nuclear  paralysis.  This  is 
especially  true  of  diphtheria.  Influenza  is  also  influential  in  the 
same  way,  and  exanthematous  diseases  are  said  to  have  induced 
nuclear  paralysis. 

Poisons  from  toxic  substances  introduced  into  the  system  or 
generated  within  it  must  be  included  among  the  factors  of  this 
category.  Xicotine,  lead,  and  other  toxins  have  been  shown  to  be 
agents  in  this  direction,  and  illuminating  gas1  has  been  shown  to 
be  another. 

Among  the  deleterious  influences  from  within,  Dr.  H.  (John 
reports  nuclear  paralysis  from  diabetes. 

The  conditions  mentioned  are  only  examples  of  many  forms  of 
inducing  factors  in  this  category  which  might  be  mentioned. 


SECTION  LXIX. 

FASCICULAR  PARALYSIS. 

Much  the  same  forms  of  paralysis  as  those  which  occur  from 
changes  in  the  nuclear  masses  may  follow  injury  in  the  course  of  the 
fibers  which  pass  from  the  nuclear  cells  to  form  the  trunks  of  the 
nerves  supplying  the  eye  muscles.  Pressure,  degeneration,  localized 
hemorrhage,  or  inflammatory  processes  may  so  impair  the  conductiv- 
ity of  these  fibers,  all  or  a  part,  that  total  or  partial  ophthalmoplegia 
may  result.  The  view  held  by  Mauthner  that  all  such  paralyses  as 
those  mentioned  in  connection  with  nuclear  disability  must  be  traced 
to  that  source  is  shown  by  such  cases  as  that  mentioned  at  page  480 
to  be  incorrect,  for  in  that  case  the  conditions  of  paralysis  which 
would  naturally  direct  attention  to  a  nuclear  affection  were  located 
even  further  from  the  nuclear  masses  than  are  the  connecting  fibers, 
being  situated  in  the  trunk  of  the  nerve  itself. 

It  is  unnecessary  to  suggest  all  the  agencies  through  which  this 
part  of  the  nervous  supply  of  the  eye  muscles  may  suffer.  The  causes 
already  mentioned  may  in  general  be  similar  in  both  classes.  Single 


r.  H.  Knapp:      Archives  of  Ophthalmologie,  vol.  viii,  p.  493. 


484  COLYTROPIA. 

symptoms  or  the  grouping  of  symptoms  in  an  individual  case  may 
perhaps  enable  a  diagnosis  to  be  made. 

Some  of  the  ultimate  causes  for  the  injury  or  destruction  of 
the  nuclear  cells  or  the  connecting  fibers  have  already  been  suggested. 
Tuberculosis,  tabes,  syphilis,  meningitis,  diphtheria,  toxic  agencies, 
atheromatous  conditions  of  the  cerebral  arteries,  trauma,  and  alco- 
holism are  among  these  ultimate  causes. 

The  trunks  of  the  third,  fourth,  and  sixth  nerves  as  they  pass 
through  the  cavernous  sinus  may  be  subject  to  pressure,  to  inflam- 
mation, degeneration,  and  other  influences  which  may  induce  paral- 
ysis. 

Attention  was  called  by  Panas,  of  Paris,1  to  the  intimate  relation 
between  fracture  of  the  petrous  bone  and  paralysis  of  the  sixth  (ab- 
ducens)  nerve.  Later,  Dr.  0.  Purtscher,  of  Klagenburt,  collected 
reports  of  a  very  considerable  number  of  cases  in  which  basilar  frac- 
ture had  been  succeeded  by  paralysis  of  the  abducens.2  Later  still, 
Friedenwald  collected  a  number  of  more  recent  cases  of  basal  frac- 
ture with  the  same  paralysis.3  In  several  of  these  cases  the  nerve 
had  been  torn  in  connection  with  the  fracture.  In  other  cases  the 
nerve  was  compressed  by  a  clot.  In  some  of  these  later  cases  the 
paralysis  was  delayed  some  days  after  the  injury.  Panas,  at  the 
International  Congress  of  Ophthalmology  of  1894,  sums  up  his  con- 
clusions respecting  basilar  fractures  and  ocular  paralyses  as  follows : — 

1.  Most  traumatic  ocular  paralyses  depend  on  basal  fracture. 

2.  The  absence  of  fracture  of  the  bones  of  the  vault  of  the  orbit 
does  not  exclude  fracture  at  the  base. 

3.  The  compression  is  from  the  fracture  itself  or  from  blood 
extravasated  into  the  cranium.     In  the  first  case  the  paralysis  is  more 
or  less  immediate ;    in  the  second  it  may  show  itself  only  after  some 
time. 

Traumatic  paralysis  or  obstruction  of  other  ocular  muscles  may 
occur  as  the  result  of  haemorrhage  within  the  sheaths  of  the  muscles 
or  of  hremorrhagic  pressure  upon  branches  of  nerves  as  well  as  rup- 
ture or  injury  of  the  muscle  or  nerve. 


1  Translated  by  Dr.  Harry  Friedenwald,  in  Archives  of  Ophthalmology,, 
vol.  xxiii,  No.  4. 

2  Archives  of  Ophthalmology,  1894,  p.  403. 
•Archives  d'Ophthalmologie,  1881. 


OBSTRUCTIVE  COLYTROPIA.  485 

PERIPHERAL  PARALYSIS. 

After  reaching  the  orbit  there  are  still  many  forms  of  disease 
or  injury  which  may  interfere  with  their  function. 

From  pure  affections  of  the  nerves  we  are  much  more  likely  to 
find  isolated  paralyses  from  causes  within  the  orbit  than  from  inter- 
cranial  causes.  A  paralysis  of  the  externus  or  of  the  internus  muscle 
not  unfrequently  occurs  from  peripheral  nerve  disabilities.  Yet,  it  is 
not  generally  safe  to  assume  that  an  isolated  paralysis  is  of  peripheral 
origin. 

In  three  cases  under  my  own  observation  the  patients  consulted 
me  in  regard  to  sudden  attacks  of  diplopia,  in  each  of  which  paralysis 
of  the  superior  rectus  muscle,  with  no  other  apparent  disability,  was 
found.  Each  improved  while  under  treatment,  but  in  each  case  the 
patients  succumbed  within  a  few  months,  one  to  abscess  of  the  brain, 
the  other  two  to  cerebral  tumor. 

There  are,  however,  cases  in  which  the  diagnosis  of  peripheral 
paralysis  is  less  difficult.  A  patient  takes  a  long  drive  in  a  severe 
wind  and  on  the  following  day  has  diplopia.  It  may  be  assumed  that 
the  peripheral  nerves  have  experienced  a  change  from  the  atmos- 
pheric conditions.  There  are  many  contingencies  of  this  kind,  each 
of  which  must  be  judged  upon  its  own  special  characteristics  and 
antecedents. 


SECTION  LXX. 
OBSTRUCTIVE  COLYTROPIA. 

The  forms  of  paralysis  which  Mauthner  calls  orbital  paralyses, 
are  mostly  of  the  class  of  obstructions. 

A  tumor  at  the  base  of  the  orbit  might  limit  or  abolish  the 
movements  of  the  eye.  Such  a  limitation  would,  except  in  the  most 
unusual  cases,  be  confined  to  the  movements  of  a  single  eye.  Exten- 
sive haemorrhage  might  have  a  similar  restrictive  effect,  as  might  also 
a  tenonitis,  an  abscess,  or  periostitis.  Tumors  of  the  bony  wall  of 
the  orbit,  in  a  nasal  cavity  or  other  neighboring  cavities,  may  also 
obstruct  the  ocular  movements.  In  most  of  the  cases  of  these  classes 
the  diagnosis  between  paralysis  and  obstruction  can  be  made.  The 
exophthalmos  from  tumors  situated  behind  the  eyeball,  the  protrusion 
of  the  tissues  at  the  side  of  the  eye  in  periostitis,  the  cedema  accom- 


486  COLYTROPIA. 

panying  haemorrhage,  and  the  palpation  of  abscess  are  among  the 
diagnostic  means. 

Among  the  most  common  sources  of  obstruction  within  the  orbit 
may  be  mentioned  periostitic  swellings,  usually  of  syphilitic  origin, 
and  which  occur  more  frequently  than  elsewhere  in  the  roof  of  the 
orbit.  The  eye  is  generally  pressed  forward  and  depressed  while  its 
movements  upward  and  from  side  to  side  are  restricted.  In  many 
of  these  cases,  by  pressing  the  end  of  the  finger  between  the  eye  and 
the  roof  of  the  orbit,  the  tumor,  painful  to  the  patient,  may  be  felt 
by  the  surgeon. 

Gummous  tumors  may  also  occupy  the  connective  tissues  of  the 
orbit.  Walter1  reports  a  case  in  which  such  gummata  occupied  both 
orbits  and  so  completely  invaded  the  muscles  themselves  that  these 
could  not  be  seen. 

So  also  these  syphilitic  periostitic  affections  may  at  length  affect 
the  bony  walls,  inducing  caries  and  necrosis.  Gummata  sometimes 
force  their  way  through  the  superior  orbital  fissure  and  involve  the 
muscles  as  though  originating  in  the  orbital  cavity. 


SECTIOX  LXXI. 
TRAUMATIC   COLYTROPIA. 

These  follow  various  forms  of  injury.  A  fracture  of  the  border 
of  the  orbit,  penetrating  wounds  and  more  frequently  than  other  trau- 
matic causes,  the  unskillful  severance  of  a  tendon  in  operations  for 
strabismus,  are  examples  of  this  form  of  obstruction,  without  paral- 
ysis of  the  nerves. 

Among  the  reported  cases  of  paralysis  of  the  inferior  oblique  is 
one  of  injury  of  the  lower  border  of  the  orbit  in  which  the  reported 
conditions  would  indicate  that  the  inferior  oblique  was  quite  intact, 
the  injury  being  to  the  insertion  of  the  inferior  rectus. 


1  Klin.  Monatsbl.  fur  Augeriheilkunde,  xxxiii,  p.  8. 


ARRESTED  DEVELOPMENT.  487 


SECTION  LXXII. 

ARRESTED  DEVELOPMENT  OF  OCULAR  MUSCLES. 

Cases  are  occasionally  met  with  in  which  anatomical  examina- 
tions have  shown  that  there  has  been,  to  a  greater  or  less  extent,  an 
arrest  of  development. 

Conditions  of  limitations  of  the  rotations  of  both  abducens  mus- 
cles of  congenital  origin,  in  which  each  of  the  external  recti  have 
been  incapable  of  inducing  rotation  beyond  the  median  plane,  have 
been  reported  by  a  number  of  authors.  In  the  reports  of  the  great 
majority  of  these  cases  there  is  such  an  absence  of  essential  data  that 
no  conclusion  can  be  drawn  from  them  as  to  the  nature  of  the  defect, 
except  in  a  few  instances  where  post-mortem  examinations  have 
shown  absence  or  arrested  development  of  a  greater  or  less  number  of 
the  eye  muscles. 

The  conditions  associated  with  or  which  may  be  the  causes  of 
most  of  the  cases  of  congenital  parah'sis  of  both  abducentes  or  of 
these  and  other  muscles,  or  indeed  of  either  of  the  eye  muscles,  may 
be  summed  up  nearly  as  follows: — 

In  a  certain  group  there  is  a  general  rachitic  state  in  which  the 
muscles  or  the  nerve  centers  or  both  participate. 

In  a  second  there  may  be  such  anomalous  insertions  of  the  ten- 
dons that  with  well-developed  and  healthy  muscles  there  may  be 
found  mechanical  obstructions  to  movement  in  certain  directions. 

In  a  third  group  the  origin  is  to  be  found  in  injuries  suffered 
at  birth. 

In  yet  a  fourth  group  the  muscle  body  is  formed,  not  of  true 
muscle  fiber,  but  of  connective  tissue.1 


1  Leszinski  reports  "congenital  absence  of  the  outward,  movements  of 
both  eyes,"  with  a  valuable  resume  of  the  bibliography  (New  York  Medical 
Journal,  February  27,  1897).  Lawford  mentions  a  case  of  a  man  who  had 
congenital  deviation  of  each  eye  to  the  right.  Post-mortem  examination 
showed  that  the  internus  of  the  right  eye  was  absent  and  the  external  rectus 
of  the  left  was  imperfectly  developed  (Ophthalmologic  Review,  1887).  Uhtoff, 
a  case  of  congenital  squint  in  which  the  external  rectus  was  replaced  by  a 
connective  cord  with  normal  insertion  (Jahrb.  fiir  Ophthal.,  1882).  Harles: 
"Absence  of  Obliques."  Archiv.  fiir  Physiol.,  Bd.  iv,  23.  Dr.  Edward  Stieren 
reports  (American  Medicine,  April  11,  1903)  the  case  of  a  child,  aged  6,  with 
inability  to  direct  the  eyes  downward.  Under  the  influence  of  local  anaes- 
thetics the  lower  ocular  conjunctiva  of  one  eye  was  freely  incised.  Careful 
examination  aided  by  a  small  strabismus  hook  failed  to  reveal  "the  slightest 
rudiments  of  an  inferior  muscle." 


488  COLYTROPIA. 

SECTION  LXXIII. 

TREATMENT  OF  COLYTROPIA. 

The  treatment  of  ophthalmoplegia  should  depend  on  the  nature 
of  the  ultimate  cause.  A  syphilitic  gumma  may  be  reduced  by  ap- 
propriate treatment,  and  similar  indications  must  govern  in  other 
cases,  though  there  may  not  be  in  all  cases  equally  favorable  prog- 
nosis. In  fact,  the  prognosis  is  generally  bad. 

Cases    of    peripheral    paralysis    often    recover    spontaneously. 

Strychnine,  electricity,  potassium  iodide,  and  a  variety  of  reme- 
dies have  been  used  with  probably  about  equal  results.  The  purely 
peripheral  cases  get  better,  the  others  usually  do  not.  It  is  self- 
evident  that  circumstances  and  environments  which  tend  to  a  better- 
ment of  the  general  health  offer  greater  encouragement  than  more 
depressing  circumstances. 

In  cases  of  alcohol  or  nicotine  poisoning,  strychnine  is  especially 
indicated. 

In  slightly  paretic  cases  a  prism  may  afford  material  relief,  and 

such  exercises  by  prisms  as  those  mentioned  at  Section  XLV  may 
be  of  service. 

Surgical  treatment  can  only  be  available  as  an  aid  for  cosmetic 
purposes.  A  very  considerable  contraction  of  a  paralyzed  internus 
may  help  to  conceal  an  unpleasant  deformity.  It  will  not  restore 
single  binocular  vision  except  within  very  narrow  limits.  The  prac- 
tice which  is  sometimes  adopted  of  performing  a  complete  tenotomy 
of  an  opposing  muscle  is  of  course  to  be  unqualifiedly  condemned. 
The  surgeon  is  not  warranted  in  disabling  an  external  rectus  because 
the  internal  rectus  is  already  disabled. 

A  ground  glass  before  the  disabled  eye  furnishes  the  most  effec- 
tive means  of  relief  to  the  diplopia  in  the  least  conspicuous  manner. 


IOT3EX. 


Abducens  nerve,  75 
Abduction,  279 
Accidental  images,  115 
Accommodation     and     axial     adjust- 
ments, 257 

and  convergence,  397 
Action   of  paralyzed  muscles,   limita- 
tion of,  469 
Adduction,  279 
Ailerons,  ligamentous,  67 
Amblyopia  of  strabismus,  361 

ex  anopsia,  369 

Amphibious  reptiles,  eye  muscles,  31 
Anatomy  of  ocular  muscles,  28 
Angle,  alpha,  372 

ascentional,  92 

facial,  211 

lateral,  93 
Anomalous  conditions,  degrees  of,  258 

less  than  strabismus,  14,  214 

not    consistent    with    physiological 
state,  444 

of  strabismus,  354 
Anophoria,  215 

and  carriage  of  head,  314 

and  consumption,  221 

and  declination,  312 

and  trachoma,  313 

definition  of,  215 

exposition  of,  219 

operations  for,  345 

treatment  of,  231 
Anotropia,  388 

declination  with,  390 

definition  of,  215 

determination  of,  392 

deviations  from,  389 

esotropia  from,  392 

illustrations  of,  391 
Antipathy  to  single  vision,  426 
Apparent     vertical     and     horizontal 
meridians,  194 

determination  of,  196 
Arteries,  basilar  and  branches,  85 

of  the  muscles,  69 

of  pons  Varolii  and  mid  brain,  85 
Asthenopia,  muscular,  18 
Astigmatism  and  myopia,  251 
Asymmetry  of  face,  320 
Attention  controlled  by  practice,  128 


Axial     adjustments,     accommodative, 
257 

Bell's  experiments  on  animals,  7 
Birds,  eye  muscles,  32 
Brachycephalic  skull,  205 
Bridles,  67 

Calipers,  Broca's,  206 
Capsule  of  Tenon,,  61 

in  strabismus  operation,  63 
Carriage  of  head  with  anomalous  con- 
ditions, 191,  221,  254,  302,  311, 
314 

Carriage  of  body,  see  carriage  of  head. 
Categories  of  paralysis,  445 
Center  of  rotation,  87 
Center  of  similitude,  86 
Cephalic  index,  43,  205 
Cerebral  localization.  448 
Choanoideus  muscle  in  batrachians,  30 

in  mammals,  33 

in  sheep,  34 

Classification     of     anomalous     condi- 
tions, 214 

of  crania,  205 
Clinical     features     of    non-strabismic 

anomalies,  306 
Clinoscope,  description  of,  237 

lens,  238 

method  of  testing,  240 

method  of  using,  239 

objectives  for,  197 

suggestion  of,  21 
Colytropia,  444 

treatment  of,  488 
Comparative  anatomy  of  eye  muscles, 

29 
Consumption  and  adjustment  of  eyes, 

25,  191 
Convergence,  absence  of,  447 

and  accommodation,  397 

in  estimating  distance,  129 
Convex  glasses  as  prisms,  400 
Corresponding  points,  166 
Cortex,  lesions  in  oculo-motor  paral- 
ysis, 446 

and  nuclei  of  oculo-motor  nerve,  83 
Cortical    region    for    impulse    to    eye 
muscles,  447 

(489) 


490 


INDEX. 


Craniostat,  Stevens's,  45,  208 
Crania,  types  of,  42,  205 

Declinations,  233 

and  heterophoria,  23,  243 

and  strabismus,  248 

and  torsions,  108,  237 

classification  of,  215 

definition  of,  235 

doctrine  of,  22 

expression  of  face  from,  252 

instruments  for  determining,  237 

local  symptoms  of,  249 

operative  treatment  for,  340 

pose  of  head  from,  254 

results  of  examinations,  241 

scheme  of  relations,  245 
Development,  arrest  of,  445,  487 
Deviations,  determination  of,  196 

in  exclusion,  285,  371 

measurements  of,  469 

of  horizontal  meridians,  194 

of  paralysis,  469 
Diplopia,  analytical  key  to,  466 

caused  by  prisms,  264 

heteronymous,  364 

homonymous,  364 

monocular,  366 

tests  by,  376 

vertical,  365,  375,  385 
Diameters  of  eyeball,  89 
Direction  of  influence  of  ocular  mus- 
cles, 93 

Directions  of  planes  of  vision,  203 
Divergence  of  retinal  meridians,  235 
Dolichocephalic  cranium,  205 

Equilibrium,  21,  260 
Esophoria,  215,  286 

and  abduction,  287 

and  anophoria,  298 

and  blepharitis,  310 

and  declinations,  288,  300 

and  distant  disturbances,  301 

facial  expression  of,  323 

first  recognition  of,  19 

in  accommodation,  284 
Esotropia,  378 

and  hypertropia,  381 

associated  symptoms,  386 

definition  of,  116 

oblique  deviations,  380 
Estimation  of  size  of  objects,  131 
Euthyphoria,  214 
Exophoria,  215 

and  declination,  243,  299 

and  insufficiency  of  interni,  19 

discussion  of,  286 

facial  expression  of.  323 

in  accommodation,  284,  290 


Exotropia,  216 

compound  deviations  in,  383 

description  of,  288 

rotations  in,  383 
Expositions  of  classes,  217 
Expressions,  facial,  from  conditions  of 
eye  muscles,  318 

from  declinations,  252 
Extendo-contraction,  241 
External  capsule,  65 
External  rectus  muscle,  51 

paralysis  of,  455 

Eye  muscles   of  amphibious   animals, 
30 

of  birds,  32 

of  fishes,  29 

of  mammals,  33 

Facial  angle,  207 
Facial  expression,  252,  318 
Field  of  binocular  vision,  165 
Fishes,  eye  muscles  of,  29 
French  Academy  of  Sciences,  10 

Goniometer,  Stevens's,  207 
Gyrus  angularis,  83 

Heterophoria,  215,  261 

and  insufficiency  of  the  interni,  20 

development  of  system  of,  18 

historical  notes  of,  14 

methods  of  examination  in,  272 

nature  and  causes  of,  297 

operative  treatment  of,  347 

relation  to  declinations,  245 

time  for  attending  to,  271 
Heterotropia,  216 

relation  to  declinations,  248 

divisions  of,  378 
Horopter,  178 

subjective,  181 
Hyperesophoria,  216 
Hyperesotropia,  216 
Hyperexophoria,  216 
Hyperexotropia,  216 
Hyperphoria,  215 

general  description,  291 

not  previously  described.  19 

vision  in,  293 
Hypertropia,  216,  378,  384 

amblyopia  of,  387 

associated  with  esotropia,  381 

not  always  noticeable,  385 

percentage  of  cases,  386 

symptoms,  386 

Illusions,  visual,  131 
Bering's,  133 
Lehmann's,  136 


INDEX. 


491 


Illusions,  Miiller-Lyer,   132 

of  height  and  breadth,  132 

Poggendorff's,  137 

Wundfs,  132 

Zb'Ilner's,  133 
Images,  accidental,  113 

multiple,  366 

Incoordinate  movements,  446 
Index,  cephalic,  43 

orbital,  40 
Inferior  oblique  muscle,  53 

paralysis  of,  464 
Inferior  rectus  muscle,  51 

paralysis  of,  464 
Insufficiency  of  the  externi,  19 
Insufficiency  of  the  interni,  14,  283 
Instruments,  Stevens's,  343 
Internal  capsule,  64 
Internal  rectus  muscle,  50 

paralysis  of,  457 
Interorbital  distance,  42,  46 
Irradiation,  136 

Katophoria,  215,  222 

and  carriage  of  head,  315 

and  declinations,  312 

operations  for,  345 

treatment  of,  231 
Katotropia,  215,  223,  388 

and  declinations,  390 

deviations  in,  389 

Law  of  Listing,  111,  183,  195,  260 

Law  of  torsions,  113,  115,  185 

Law  of  unconscious  conclusions,  176 

Leaning  of  corneal  meridians,  123 

Lens,  stenopaic,  227 

Limitation    of    action    of    paralyzed 

muscles,  469 
Line,  visual,  92 

median,  92 

base,  92 

Mammals,  eye  muscles  of,  33 
Memorandum,  blank  for,  305 
Mesocephalic  cranium,  205 
Method  of  determining  axes  of  orbit, 

208 

Motor  areas  for  eye  movements,  448 
Movements  of  the  eyes,  28 

associated,  103 

Movements  of  globe,  center  of,  86 
Muscles,  motor,  of  the  eyes,  48 
Muscular  consciousness,  125 
Mydriatics    and    apparent    hyperme- 

tropia,  399 
influence  of  in  correcting  deviations, 

402 
Myopia  and  declination,  250 


Nerves  of  the  ocular  muscles,  71 

abducens,  75 

distribution  of,  72 

nuclear  origin  of,  76 

oculo-motor,  72 

trochlear,  74 
Normal  directions  of  planes  of  vision, 

203 
Nuclear  cell  groups,  79 

circulation  to,  84 

connection  with  cortex,  82 
Nuclear  paralysis,  470 
Nystagmus,  436 

in  cortical  disease,  439 

of  hysteria,  439 

of  miners,  440 

treatment  of,  442 

Obstruction,  445,  485 
Oculo-motor  nerve,  71 
Ophthalmic  artery,   70 

vein,  70 

Ophthalmometer  of  Helmholtz,  88 
Ophthalmotrope,  Stevens's,  114 
Ophthalmoplegia  externa,  476 

interna,  476 

locality  of  lesion,  478 

total,  476 
Optic  axes,  44 

in  ethnology,  46 

method  of  ascertaining,  45 

plane  of,  44 

Orbital    angle    in    comparative    anat- 
omy, 47 

in  man,  42 
Orbital  muscles,  67 
Orbito-ocular  aponeurosis,  61 
Orbits,  35 

axes  of,  41 

bases  of,  46 

borders  of,  39 

characteristic  forms  of,  44 

comparative  index  of,  46 

determination  of  axes,  208 

external  wall  of,  37 

form  of  in  relation  to  cranium,  209 

influence  on  declinations,  407 

measurements  of,  39 
Orthophoria,  215,  261 

Paralysis,  445,  452 

aetiology  of  nuclear,  479 

cases  of,  456,  458 

causes  of  nuclear,  479 

diplopia  of,  453 

forms  of,  452 

key  to  relations  of  double  images, 

466 
nuclear,  470 


492 


INDEX. 


Paralysis,     objective     manifestations 
of,  466 

of  external  rectus,  455 

of  inferior  oblique,  464 

of  inferior  rectus,  460 

of  internal  rectus,  457 

of  oculo-motor  nerve,  474 

of  superior  oblique,  460 

of  superior  rectus,  457 

rotations  and  leanings  in,  462 
Perception  of  space,  visual,  125 
Perspective,  137 
Phorometer,  273 
Physiology,  86 
Plagiotropia,  120 
Planes  of  head,  90 

of  action  of  muscles,  94 

of  vision,  normal,  200 
Position  of  eyes  in  animals,  28 
Prism,  vertical,  in  strabismus,  400 
Procedure  in  examinations,  302 
Pseudoscope,  151 
Psychic  colytropia,  450 
Psychical  elements  in  vision,  130 
Psychological      laboratories,      investi- 
gations in,  127 
Ptosis,  447 

Raddrehungawinkel,  93 

Regard,  field,  line,  plane  and  point  of, 

92 
Relation  of  plane  of  vision  to  cranium, 

214 

of  visual  lines  to  each  other,  215 
Rod  test  of  Maddox,  276 
Rotations  of  the  eyes,  225 
center  of,  87 

determination  of  extent,  225 
in  converging  strabismus,  403 
in  relation  to  adjustments  of  eyes, 

221 

in  relation  to  plane  of  vision,  210 
standards  of,  230 

Sections  of  cranium,  91 

Size  of  objects,  visual  perception  of, 

131 

Space,  visual  perception  of,  124 
Spasm,  division  of  colytropia,  445 
Squint,  secondary,  405,  469 
Stereoscope,  143 

of  Brewster,  145 

of  Helmholtz,  145 

of  Landolt,  149 

of  Wheatstone,  143 
Stereostroboscope,  151 
Strabismus,  354 

amblyopia  of,  361,  368 

and  hypermetropia,  397 


Strabismus  and  myopia,  397 

Bell's  experiments  on,  7 

causes  of,  395 

concomitant,  356 

deviations  of,  371,  404 

diplopia  of,  362 

disappearance  of  during  sleep,  404 

diverging  converted   to   converging, 
432 

doctrine  of  Bonders,  13,  397 

double  vertical,  388 

early  operations  for,  9 

effect  on  carriage  of  body,  358 

effect  on  health,  357 

effect  on  vision,  357 

glasses  used  for,  416 

heredity  of,  407 

historical  notes  of,  1 

multiple  images  in,  366 

object  of  operations,  418 

oblique  deviations,  359 

one  eye  selected  for  fixation,  358 

operations  by  Dieffenbach,  10 

operations  by  Graefe,  12,  350 

operations  by  Listen,  11 

operations  by  Lucas,  10 

operations  by  Taylor,  4 

paralytic,  356 

periodic  or  intercurrent,  393 

prophylactic  methods  against,  415 

results  of  treatment,  422 

resume  of  treatment,  423 

table  of  cases,  408 

tests  by  diplopia,  373 

tests  by  exclusion,  372 

tests  by  Bering's  method,  377 

tests  by  stereoscope,  376 

treatise  by  Taylor,  4 

treatment  of,  414 

treatment  of  by  empirical  method, 
421 

treatment    of   bv   rational   method, 
419 

views  concerning,  1 
Subjective  horopter,  181 
Superior  oblique  muscle,  52 

paralysis  of,  460 
Superior  rectus  muscle,  51 

paralysis  of,  457 
Sursumduction.  279 
Synopsis  of  classification,  214 

Talantropia,  437 

of  miners,  440 

treatment  of,  442 
Tendons,  breadth  of  insertions,  54 

design  indicating  insertions,  59 

distances  from  corneal  border,  57 

Fuch's  study  of,  55 


INDEX. 


493 


Tendons,  insertions   and  declinations, 
406 

variations  of  insertions,  58 
Tendon  contraction,  352 
Tenotomies,  graduated,  348 

by  Graefe,  350 

by  Guerin,  9 
Terms,  definition  of,  90 
Test  letters  of  Snellen,  129 
Tests,  auxiliary  in  heterophoria,  278 
Torsions,  definition  of,  93 

law  of,  113,  115 

law  of  adjustments,  120 

method  of  testing,  201 

not  to  be  confounded  with  declina- 
tions, 108,  218 

phenomena,  causes  and  laws  of,  10G 

positive  and  negative,  108 

stereoscopic  diagram  indicating,  123 

voluntary,  200 

well  defined  meaning  of,  242 
Torticollis  from  hyperphoria  and  de- 
clinations, 302 
Trauma,  division   of   colytropia,   445, 

486 

Treatment    of    non-strabismic    anom- 
alies, 327 

by  decentering  glasses,  334 

by  gymnastics  by  prisms,  330 

by  prisms  as  spectacles,  333 

by  tonics  and  change,  328 

surgical,  321,  338 


Trochlear  nerve,  74 
Tropometer,  225 

examination  by,  227 

influence  on  doctrine  of  anomalies, 
24 

scale  for,  227 
Types  of  crania,  209 


Unconscious  conclusions,  153 

Veins  of  the  muscles,  70 

Vessels  supplying  muscles  of  the  eye, 

69 

Vertical  meridians,  apparent,  194 
determination  of  positions,  197 
positions  with  different  adjustments 

of  eye,  99 
Vertical  tensions  and  declinations  in 

strabismus,  61 
Visual  angle,  129 
Visual  perception  of  space,  124 
binocular  vision  in,  142 
conditions  according  to  Helmholtz, 

125 

illumination  an  element  in,  140 
mental  process  in,  138 
role  of  convergence  in,  129 


Word  blindness,  division  of  colytropia, 
445,  450 


INDEX  OF  AUTHOES. 


j'Egineta  (Paulus).  Mask  for  strabis- 
mus, 2 

Allen.  On  fourth  nerve,  75.  On  sixth 
nerve,  76 

Arata.     Drawing  of  sheep's  eye,  76 

d'Astros.  Blood  supply  of  nuclei  of 
motor  nerves,  473 

Barrow.     Center  of  motion  of  eye,  86 

Baudens.  Operation  for  strabismus, 
415 

Baudrus.     Capsule  of  Tenon,  63 

Baumgarten.  Muscle  replaced  by  con- 
nective tissue,  457 

Beevor.    Cerebral  localization,  447,  448 

Bell  (Sir  Charles).  Experiments  on 
ocular  muscles  of  animals,  7 

Bell  (J.  D.).     Nystagmus,  438 

Benedikt.  Measurement  of  crania, 
211 

Bernheimer.  Nucleus  of  third  nerve, 
77,  83,  472.  Nystagmus,  442. 
Motor  nerve  supply,  447 

Bohm.     Periodic  strabismus,  393 

Bonnet.  Capsule  of  Tenon,  63.  Oper- 
ation for  strabismus,  414 

Bouillaud.     Cerebral  localization,  44S 

Bourdon.  Visual  perception  of  space, 
129 

Boyer  (Arthur  A.).  Drugs  in  func- 
tional nervous  disorders,  330 

Boyer  (Lucien).  Quotation  from  Le 
Cat,  5.  Muscles  and  capsule,  63. 
Strabismus,  359,  414 

Brewster.     Stereoscope,  145 

Broca.  Measurements  of  orbits,  40. 
Method  of  finding  orbital  axis,  44. 
Head  calipers,  207.  Cerebral  locali- 
zation, 448 

Bruce.  Origin  of  third  nerve,  72,  78, 
84 

Briick.    Unconscious  conclusions,  153 

Buffon.    Strabismus,  356 

Cameron.    Illusion,  135 

Celsus.     References  to  strabismus,  2 

Charcot.  Disseminated  nodular  scler- 
osis, 439.  Lesion  in  word  blind- 
ness, 451 

Cohn.     Nuclear  paralysis,  483 

Columbus  (Realdus).  Description  of 
Tenon's  capsule,  62 

Conkling.     Nystagmus,  438 

Court.    Nystagmus,  438 

(494) 


Crete.     Prism,  304 

Critchett.      Operation    for    tenotomy. 

350 

Cruveilhier.    Axes  of  orbits,  35 
Cunier.    Operation  for  strabismus,  414 
Cushing.        Transmission      of      nerve 

energy,  448 

Darwin  (Erasmus).    Views  on  strabis- 
mus, 3 

Deconde.    Nystagmus,  440 
Dejernine.     Lesion  in  word  blindness, 

451 
Desmarres.    Operation  for  strabismus, 

12 

Dieffenbach.      Operation    for    strabis- 
mus, 9,  359,  414 

Dix.  Operation  for  strabismus,  414 
Donders.  Doctrine  of  strabismus,  13, 
355.  Center  of  motion,  86,  89.  Ac- 
tion of  muscles,  100.  Torsions,  113. 
Accidental  images,  116.  Corres- 
ponding points,  167.  Leaning  of 
retinal  meridians,  234.  Accom- 
modation, 257.  Accommodation 
and  convergence,  397,  399.  Hyper- 
metropia  and  converging  strabis- 
mus, 416 
Dove.  Experiment  with  electric 

spark,  124,  153,  181,  183 
Doyer.    Center  of  motion,  87 
Dransart.     Nystagmus,  440 
Duane.    Parallax  test,  285,  373 
Dufour.    Nuclear  paralysis,  482 
Duret.    Circulation  to  the  nuclei,  85 
Duval.    Oculo-motor  nerve,  72 

Edinger.    Origin  of  third  nerve,  73 
Elschnig.    Circulation  of  the  eye,  70 
Emmert.    Measurements  of  crania,  41. 

Orbital  angle,  47.     Insufficiency  of 

interni  and  orbital  axes,  298 
Euclid.    Ideas  of  binocular  vision,  143 
Exner.    Cerebral  localization,  448 
Fernandio.    Nystagmus,  439 
Ferrier.    Cerebral  localization,  447,  448 
Fick.    Terminology  of  rotations,  228 
Flourens.     Cerebral  localization,  448 
Frankl-Hockwart.     Paralysis  of  third 

nerve,  480 

Fritsch.    Cerebral  localization,  448 
Fuchs.    Insertions  of  eye  muscles,  50, 

59.     Paralysis   of  superior  rectus, 

459 


INDEX  OF  AUTHORS. 


495 


Galen.  Tunica  sexta,  62.  Views  of 
binocular  vision,  143 

Galezowski.  Latent  divergent  strabis- 
mus, 18 

van  Gehucten.    On  sixth  nerve,  84 

Giraud-Teulon.  Center  of  motion,  89. 
The  horopter,  177 

Golz.    Cerebral  localization,  448. 

von  Graefe.  Strabismus,  12.  Insuf- 
ficiency of  the  interni,  14,  282,  284, 
290,  291,  302,  356.  Insufficiency  of 
the  externi,  19.  Equilibrium,  21. 
Abduction  and  Adduction,  279. 
Gymnastics  with  prisms,  330.  Treat- 
ment of  asthenopia,  337.  Opera- 
tion for  tenotomy,  350.  Deviation 
in  strabismus,  359,  360,  404.  Anti- 
pathy to  single  vision,  377,  426. 
Periodic  strabismus,  393.  Squint 
and  expression  of  disease,  396.  Ac- 
commodation in  paralysis,  398. 
Treatment  of  strabismus,  415. 
Nystagmus,  438,  440,  441 

Grossman.    Accidental  images,  119 

van  Gudden.    Oculo-motor  nerve,  72 

Guerin.     Tenotomies,  9 

Harles.     Absence  of  obliques,  487 

Hasse.    Asymmetry  of  skull,  320 

Helmholtz.  Retinal  meridians,  22, 
194,  199,  202,  234,  235.  Center  of 
motion,  86.  Divisions  of  the  head, 
90,  93.  Torsions,  99,  100,  107,  115. 
Accidental  images,  117,  122.  Mus- 
cular consciousness,  125.  Illusions, 
134,  135.  Stereoscope,  145,  148. 
Corresponding  points,  167,  169,  176. 
The  horopter,  177,  180,  184 

Henly.    Divisions  of  the  head,  90 

Hensen.    On  third  nerve,  74,  79 

Hering.  Action  of  muscles,  94.  Illu- 
sion, 133,  134.  Corresponding 
points,  166.  The  horopter,  180. 
Retinal  meridians,  195.  198,  234. 
Experiment  with  falling  bodies, 
377.  Test  of  strabismus,  423 

Hess.  Accommodation  and  converg- 
ence, 398 

Heuerman.     Claims  of  John  Taylor,  5 

Hewitson.    Nystagmus,  438 

Hippocrates.  Distortion  of  eyes  from 
epilepsy,  1 

Hitzig.    Cerebral  localization,  447,  448 

Hook.     Visual  angle,  128 

Horsley.  Cerebral  localization,  447, 
448 

Hunter.  Amblyopia  in  strabismus, 
371 

Hutchinson.  Total  ophthalmoplegia, 
471 


Jackson.     Cerebral  localization,  449 
Johnson.      Amblyopia  in    strabismus, 

369 
Judd.    Illusion,  135 

Kahler.     On  third  nerve,  80 
Knapp.     Causes  of  paralysis,  483 
Kolliker.     Measurements      of     cones, 

129 

Krause.    Fibers  in  third  nerve,  71 
Kussmaul.     Word  blindness,  450 

Laborde.     Oculo-motor  nerve,  72 

Ladd.  Transmission  of  nerve  energy, 
448 

Landolt.  Insufficiency  of  the  interni, 
18.  Stereoscope,  149 

Lawford.  Congenital  absence  of  mus- 
cles, 487 

Lawrence.  Deviation  in  strabismus, 
360 

Lebreich.  Operation  for  tenotomy, 
350 

Le  Cat.  Description  of  John  Taylor,  5 

Le  Conte.  Torsions,  114.  Accidental 
images,  119.  Retinal  meridians, 
195,  234 

Lehman.     Illusion,  136 

Leszinski.  Congenital  absence  of  mus- 
cles, 487 

Listen.  Operation  for  strabismus,  11, 
414 

Listing.  Action  of  muscles,  100.  Law 
of,  111,  112,  183,  195,  260 

Lucas.     Operation  for  strabismus,  10 

Luschka.     Origin  of  fourth  nerve,  75 

McAllister.    The  visual  field,  135 

McKenzie.     Strabismus  operation,  11 

Maddox.    Rod  test,  276 

Maitre-Jan.     Views  of  strabismus,  2 

Malgaigne.    Capsule  of  Tenon,  63 

Marina.    Nucleus  of  third  nerve,  83 

Mauthner.  Nuclei  of  ocular  nerves, 
80,  478.  Center  of  motion,  89.  Ac- 
tion of  muscles,  97,  100.  Torsions, 
106,  114.  Paralysis  of  ocular  mus- 
cles, 444,  446,  459,  463.  Nuclear 
paralysis,  483.  Orbital  paralysis, 
485 

Meisner.     Retinal  meridians,  195. 

Merkel.     Fibers  in  fourth  nerve. 

Meyer.    Ophthalmic  artery,  69. 

Mobius.     Nuclear  centers,  474. 

Van  Moll.    Corresponding  points,  167. 

Motais.  Origin  of  Choanoideus  mus- 
cle, 33.  Capsule  of  Tenon,  64.  Lig- 
amentous  ailerons,  67. 

Muller  (H.).    Orbital  muscle,  69. 

Miiller  (J.  J.).  Center  of  motion,  86. 
Subjective  images,  166. 


496 


INDEX  OF  AUTHORS. 


Miiller-Lyer.    Illusion,  132,  135. 
Munk.     Cerebral  localization,  448. 
Miinsterberg.     Stereostroboscope,  150. 

Nagel.    Voluntary  torsions,  201. 
Nettleship.    Nystagmus,  437. 
Nieden.     Nystagmus.  440. 
Noel.     Nystagmus,  440. 
Nothnagel.    Cerebral  localization,  451. 
Nusslmum.     On  third  nerve,  72. 

Obersteiner.     On  third  nerve,  80. 

Panas.  Paralysis  of  superior  rectus, 
455,  459.  Fascicular  paralysis,  484. 

Pare  (Ambroise).  .-Etiology  of  stra- 
bismus, 2. 

Parinaud.     Spasm,  447 

Perlia.    Nucleus  of  third  nerve,  77,  £0. 

Pick.     On  third  nerve,  80. 

PoggendorfT.     Illusion,  13o. 

Prentice.    Prism  diopter.  334. 

Purkinje.     Subjective  images,  106. 

Purtscher.     Fascicular  paralysis,  484. 

Reuss.     Nystagmus,  438. 
Keute.     Accidental  images,   115.     Ac- 
tion of  muscles,  97,  100. 
Rossi.    Strabismus,  4. 

Sappey.  Axes  of  orbits,  35.  Origin 
of  external  rectus,  51.  Ligament- 
ous  ailerons,  07. 

Schiifer.     Cerebral  localization,  448. 

Schroder.     Perspective  illusion,  139. 

Schwalbe.  Origin  of  eye-muscles,  49. 
Capsule  of  Tenon,  G4. 

Schweigger.    Muscular  asthenopia,  18. 

Serieux.  Lesion  in  word  blindness,  451. 

Snell.     Nystagmus,  438,  439. 

Snellen.    'Test  letters,  129. 

Steel.    Illusion,  135. 

Stehvag.     Insufficiency  of  interni,  18. 

Stevens.  Terminology  of  heterophoria, 
18.  Operations  for  insufficiency  of 
externi,  20.  Anomalies  of  vertical 
directions  of  optic  axes,  21.  In- 
sertions of  eye-muscles  in  sheep, 
35.  Craniostat,  45.  The  horopter, 
177.  Retinal  meridians,  194.  Vol- 
untary torsion,  201.  Planes  of  vis- 
ion, 203.  Facial  goniometer,  207. 
Method  of  determining  axis  of 
orbit,  208.  Classification  and  term- 
inology, 214,  444.  The  tropometer, 
225.  Standards  of  rotation,  230. 
The  clinoscope,  237.  The  lens  clin- 
oscope,  240.  AstigTiiatism,  myopia, 
and  declination,  251.  Facial  ex- 
pression and  bodily  pose,  252,  254, 
313,  318.  The  p'horometer,  273. 


The  stenopaic  lens,  277.  Gymnas- 
tics with  prisms,  331.  Gymnastics 
for  declination,  331.  The  rod  clin- 
oscope, 332.  Accommodation  and 
convergence,  397.  Antipathy  to 
single  vision,  427. 

Stevens  (Charles  W.).  Grooved  di- 
rector, 353.  Nystagmus,  442. 

Stieren.  Absence  of  inferior  rectus. 
487. 

Stilling.  Theory  of  compression,  43. 
On  fourth  nerve,  75. 

Stratfield.  Heredity  of  strabismus, 
407. 

Strohmeyer.  Operation  for  strabis- 
mus, 9,  359,  414. 

Taylor     (John).       Strabismus    opera- 
tion, 4,  414.     Portrait,  27. 
Tenon.     Anatomy   of   orbit,  3.      Cap- 
sule of,  62. 

Thompson.     Nystagmus,  438. 
Toldt.     Diameters  of  orbit,  40. 
Topinard.      Measurements    of    orbits, 
40. 

Uhthoff.  Muscle  replaced  by  connec- 
tive tissue,  457,  487. 

j  Valentin.  On  sixth  nerve,  76.  Center 
of  motion,  86. 

Da  Vinci  (Leonardo).  Binocular  vis- 
ion, 143. 

Virchow.    Measurements  of  orbits,  40. 

Volckers.     On  third  nerve,  74,  79. 

Volkmann.  Weight  of  internal  rec- 
tus, 50.  Center  of  motion,  86.  Ac- 
tion of  muscles,  94,  100.  Visual 
angle,  128.  Stereoscopic  images, 
147.  Corresponding  points,  167, 
169,  170.  The  horopter,  180.  Ret- 
inal meridians,  194,  202,  234 

Vulpian.  Disseminated  nodular  scler- 
osis, 439. 

Walter.    Gummata  of  orbit,  486. 

Weber.     Visual  angle,  128. 

Weiss.     Measurements   of   orbits,  40, 

46,  90.     Insertions  of  muscles,  53, 

54,  57,  406. 
Wells.       Muscular      asthenopia,      18. 

Gymnastics  with  prisms,  330.  Nys- 
tagmus, 437. 
Wheatstone.      Stereoscope,    143,    145. 

Pseudoscope,    151.      Corresponding 

points,  176. 

|    Wood.     Pseudoscope,  152. 
Wundt.     Visual   perception   of  space, 

124,  129.     Illusion,  133,  134. 

Zollner.     Illusion,   134. 

Zoth.     Asymmetry  of  skull,  320. 


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